Flywheel assembly

ABSTRACT

A flywheel assembly that transmits torque from a crankshaft of an engine is provided. The flywheel assembly has a flywheel with a friction surface and an elastic coupling mechanism. The elastic coupling mechanism elastically couples the flywheel and the crankshaft in a rotating direction, and has a pair of first disk-shaped members axially spaced from each other and fixed together, a second disk-shaped member that is arranged between the pair of first disk-shaped members, and an elastic member that elastically couples the first disk-shaped members to the second disk-shaped member in the rotating direction. Further, a plate-like coupling portion extending between outer peripheries of the paired first disk-shaped members fixes the pair of first disk-shaped members together.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 10/685,736 filed on Oct. 16, 2003, now abandoned. The entiredisclosure of U.S. patent application Ser. No. 10/685,736 is herebyincorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to a damper mechanism. Morespecifically, the present invention relates to a damper mechanism fortransmitting a torque while absorbing and damping torsional vibrations.The present invention also relates to a flywheel assembly, especially aflywheel assembly that is elastically coupled to a crankshaft in arotational direction.

2. Background Information

A clutch disk assembly used in a vehicle has a clutch function forreleasably engaging a flywheel, and a damper function for absorbing anddamping torsional vibrations transmitted from the flywheel. In general,vibrations of vehicles include idling noises (rattling noises), drivingnoises (acceleration and deceleration rattling noises and mufflednoises), and tip-in/tip-out (low-frequency vibrations). For suppressingsuch noises and vibrations, the clutch disk assembly is provided with adamper.

The idling noises are rattling noises, which are generated from atransmission when a clutch pedal is released after shifting a gearposition to neutral, e.g., to stop at a traffic light. These noises aredue to the fact that an engine torque is low and varies to a largeextent in response to engine combustion when an engine speed is in ornear an idling range. In or near the idling range, tooth collisionsoccur between an input gear and a counter gear of the transmission.

The tip-in/tip-out (low frequency vibrations) is a large longitudinalvibration of a vehicle body, which occurs when a driver rapidlydepresses or releases an acceleration pedal. If a power transmissionsystem has a low rigidity, a torque transmitted to tires is reverselytransmitted from the tires to the power transmission system. Thisreaction causes an excessive torque to be transmitted to the tires sothat large longitudinal vibrations transitionally occur to vibrate thevehicle body longitudinally to a large extent.

The idling noises are significantly affected by torsion characteristicsof a clutch disk assembly at and around a zero torque, and can beeffectively prevented by reducing a torsional rigidity at and around thezero torque. Conversely, for reducing the longitudinal vibrations of thetip-in/tip-out, torsion characteristics of the clutch disk assembly mustbe solid to a large extent.

For overcoming the above problems, a clutch disk assembly has beenprovided that uses two kinds of spring members for providingcharacteristics having two stages. In this structure, the torsionalrigidity and a hysteresis torque are kept low in the first stage (lowtorsion angle region) of the torsion characteristics. This is effectivein preventing noises during idling. Since the torsional rigidity and thehysteresis torque are kept high in the second stage (high torsion anglerange) of the torsion characteristics, the longitudinal vibrations oftip-in/tip-out can be sufficiently damped.

Further, such a damper mechanism has been known that it can effectivelyabsorb minute torsional vibrations without operating a large frictionalresistance mechanism for the second stage when the minute torsionalvibrations are applied, e.g., due to combustion variations of the enginein the second stage of the torsion characteristics.

The damper mechanism described above can be achieved by providing africtional resistance generating mechanism having the following specificstructures. The frictional resistance generating mechanism is arrangedas a whole to operate in parallel with a spring member of a highrigidity in a rotational direction, and has a frictional resistancegenerating portion, and a rotating-direction engagement portion arrangedto operate in series with respect to the frictional resistancegenerating portion in the rotational direction. The rotating-directionengagement portion has a minute rotating-direction space between twomembers.

In the prior art, the rotating-direction space can be configured tooperate in response to minute torsional vibrations only in the secondstage (large torsion angle region) of the torsion characteristics.

In some cases, however, vibration damping performance can be improved,when such a manner is employed that a large frictional resistance doesnot occur even when the torsion angle exceeds a predetermined angle inthe first stage (small torsion angle region) of the torsioncharacteristics, and thus a large frictional resistance does not occurin response to the minute torsional vibrations.

Specifically, the damper mechanism described above is achieved byproviding a frictional resistance generating mechanism having thefollowing structure. This frictional resistance generating mechanism isarranged to operate in parallel with spring members, which have a highrigidity as a whole, in the rotating direction. Further, the frictionalresistance generating mechanism has a frictional resistance generatingportion and a rotating-direction engagement portion arranged to operatein series with respect to the frictional resistance generating portionin the rotating direction. The rotating-direction engagement portion isformed of a minute rotating-direction space between two members.

Accordingly, when minute torsional vibrations caused by combustionvariations of an engine are generated, the minute rotating-directionspace prevents the operation of the frictional resistance generatingportion.

However, when torsional vibrations of a large torsion angle are applied,the frictional resistance generating portion operates, and thefrictional resistance generating portion does not operate correspondingto the minute rotating-direction space only on the opposite sides, ofthe torsion angle range. Thus, a large frictional resistance suddenlyoccurs on the opposite sides of the torsion angle range when torsionalvibrations of a large torsion angle are applied. This large frictionalresistance increases the impact of collision between the members formingthe rotating-direction space so that hitting or tapping noises occur.

In conventional damper mechanisms, a flywheel is fixed to a crankshaftof an engine for absorbing vibrations caused by combustion variations ofthe engine. Further, a clutch device is arranged on the transmissionside of the flywheel in an axial direction. The clutch device includes aclutch disk assembly coupled to an input shaft of a transmission and aclutch cover assembly for biasing a frictional coupling portion of theclutch disk assembly with the flywheel. The clutch disk assembly has adamper mechanism for absorbing and damping torsional vibrations. Thedamper mechanism has elastic members such as coil springs, which aredisposed for compression in the rotating direction.

A structure is also known such that the damper mechanism is arranged notin the clutch disk assembly but between the flywheel and the crankshaft.In this structure, the flywheel is located on an output side of avibration system, in which the coil springs provide a boundary betweenthe output and input sides, and an inertia on the output side is largerthan that in a conventional structure. Consequently, a resonancerotation speed can be set below an idling rotation speed and a highdamping performance can be achieved. The structure formed of the abovecombination of the flywheel and the damper mechanism provides theflywheel assembly or the flywheel damper.

When the flywheel assembly described above receives torque variationsfrom an engine, the springs in the damper mechanism are compressed inthe rotational direction to absorb and damp the torque variations.Further, the damper mechanism has a frictional resistance generatingmechanism formed of a plurality of members, therefore sliding occurs inthe frictional resistance generating mechanism to generate apredetermined hysteresis torque when springs are compressed.Consequently, torsional vibrations are rapidly damped.

The damper mechanism includes a pair of input plates opposed to eachother, an output plate disposed between the input plates, and a coilspring circumferentially and elastically coupling the pair of inputplates to the output plate. The pair of input plates is fixed togetherby a plurality of stop pins on the radially outer side so that the inputplates rotate together. The stop pins are inserted into recesses formedat an outer periphery of a flange. The pair of input plates can rotatethrough a predetermined angle range with respect to the flange, and therelative rotation stops when the stop pins come into contact with thecircumferential ends of the recesses. As described above, the stop pinscouple the pair of input plates together as well as function as astopper with respect to the flange.

The stop pin must have a certain diameter and must be disposed radiallyinside the outer periphery of the pair of input plates. Due to theseconditions, it is impossible to increase a relative rotation anglebetween the input plate pair and the flange in the structure employingthe stop pins. This means that the performance of coil springs cannot befully utilized even if the coil springs have a high strength because therelative rotation angle cannot be increased sufficiently. For reducingtooth-hitting noises and muffled noises of a drive system during drivingof a vehicle, it is necessary to minimize a torsional rigidity in anacceleration/deceleration torque range for setting a torsional resonancefrequency of the drive system to a value lower than an actual rotationrange. For achieving the low torsional rigidity and a further increasedstopper torque, it is necessary to ensure a wide torsion angle.

In view of the above, it will be apparent to those skilled in the artfrom this disclosure that there exists a need for an improved dampermechanism. This invention addresses this need in the art as well asother needs, which will become apparent to those skilled in the art fromthis disclosure.

SUMMARY OF THE INVENTION

An object of the present invention is to improve a torsional vibrationdamping function by generating a predetermined frictional resistance inboth of first and second stages of the torsion characteristics of adamper mechanism while preventing generation of a predeterminedfrictional resistance in response to minute torsional vibrations.

Another object of the present invention is to suppress occurrence ofhitting noises in a frictional resistance generating mechanism, which isprovided with a minute rotating-direction space for absorbing minutetorsional vibrations.

Still another object of the present invention is to overcome the problemcaused by conventional stop pins in a flywheel assembly, and to increasesufficiently a relative torsion angle between the input and outputmembers.

According to a first aspect of the present invention, a damper mechanismprovided to transmit a torque while absorbing and damping torsionalvibrations includes a first rotary member, a second rotary member, afirst elastic member, a second elastic member, a frictional resistancegenerating mechanism, and a frictional resistance suppressing mechanism.The second rotary member is rotatable relative to the first rotarymember. The first elastic member is compressed in response to relativerotation between the first and second rotary members to achieve lowrigidity characteristics in a small torsion angle region of the torsioncharacteristics. The second elastic member is compressed in response torelative rotation between the first and second rotary members to highrigidity achieve characteristics in a large torsion angle region of thetorsion characteristics. The frictional resistance generating mechanismgenerates a frictional resistance when the first elastic member is in acompressed state and when the second elastic member is in a compressedstate. The frictional resistance suppressing mechanism has arotating-direction space to prevent the frictional resistance generatingmechanism from operating in a predetermined angle range.

According to this damper mechanism, when the first and second rotarymembers rotate relatively to each other, the first and second elasticmembers are compressed, and the frictional resistance generatingmechanism generates a frictional resistance. Consequently, the torsionalvibrations are rapidly absorbed and damped. In a small torsion angleregion, the first elastic member is compressed to achieve low-rigiditycharacteristics. In a large torsion angle region, the second elasticmember is compressed to achieve the high-rigidity characteristics. Inany region, the frictional resistance generating mechanism operates togenerate the frictional resistance. However, when minute torsionalvibrations are applied, the rotating-direction space of the frictionalresistance suppressing mechanism acts to stop or prevent the operationof the frictional resistance generating mechanism in any angle range.Thus, a large frictional resistance does not occur in response to theminute torsional vibrations in a first stage of the torsioncharacteristics, therefore, torsional vibration damping performanceimproves.

According to a second aspect of the present invention, the dampermechanism of the first aspect further has a feature such that thefrictional resistance generating mechanism and the frictional resistancesuppressing mechanism are arranged to operate in parallel with the firstand second elastic members in the rotational direction.

In this damper mechanism, since the frictional resistance generatingmechanism and the frictional resistance suppressing mechanism arearranged to operate in parallel with the first and second elasticmembers in the rotational direction, these mechanisms are able tooperate when the first and second elastic members operate.

According to a third aspect, the damper mechanism of the second aspectfurther has such a feature that the first and second elastic membersoperate in series in the rotational direction.

In this damper mechanism, the first and second elastic members operatein series in the rotational direction, however, the second member ishardly compressed when the first elastic member is being compressed.

According to a fourth aspect of the present invention, the dampermechanism of the first, second, or third aspect further has a featuresuch that the frictional resistance generating mechanism realizes firstregions for increasing stepwise a frictional resistance on oppositesides of a range of the predetermined angle, respectively, and a secondregion for providing a constant frictional resistance.

In this damper mechanism, the frictional resistance increases stepwisein the first region before the large frictional resistance is generatedin the second region. Thus, a wall of a high hysteresis torque does notexist when generating the large frictional resistance. This reduceshitting or tapping noises of claws, which may occur when the dampermechanism generates a high hysteresis torque.

According to a fifth aspect of the present invention, the dampermechanism of the fourth aspect further has a feature such that thefrictional resistance generating mechanism generates an intermediatefrictional resistance in the first region.

In this damper mechanism, an intermediate frictional resistance occursin the first region before a large frictional resistance occurs in thesecond region. Thus, a wall of a high hysteresis torque does not existwhen generating the large frictional resistance. This reduces hitting ortapping noises of claws, which may occur when the damper mechanismgenerates a high hysteresis torque.

According to a sixth aspect of the present invention, the dampermechanism of the fourth aspect further has a feature such that thefrictional resistance generating mechanism generates a frictionalresistance increasing smoothly in the first region.

In this damper mechanism, a frictional resistance increasing smoothlyoccurs in the first region before a large frictional resistance occursin the second region. Thus, a wall of a high hysteresis torque does notexist when generating the large frictional resistance. This reduceshitting or tapping noises of claws, which may occur when the dampermechanism generates a high hysteresis torque.

According to a seventh aspect of the present invention, a frictionalresistance generating mechanism is arranged between two relativelyrotatable members of a rotary mechanism for generating a frictionalresistance in response to relative rotation that occurs between the twomembers by torsional vibrations to damp the torsional vibrations. Thefrictional resistance generating mechanism includes a first frictionalresistance generating portion, a second frictional resistance generatingportion, a first frictional resistance suppressing portion, and a secondfrictional resistance suppressing portion. The second frictionalresistance generating portion generates a frictional resistance largerthan that generated by the first frictional resistance generatingportion. The first frictional resistance suppressing portion has a firstrotating-direction space to prevent the operation of both of the firstand second frictional resistance generating portions. The secondfrictional resistance suppressing portion has a secondrotating-direction space to prevent the operation of only the secondfrictional resistance generating portion on the opposite sides of atorsion angle range of the first rotating-direction space.

In the frictional resistance generating mechanism, when the torsionangle of the torsional vibrations is within the torsion angle range ofthe first rotating-direction space in the first frictional resistancesuppressing portion, the first rotating-direction space prevents theoperation of the first and second frictional resistance generatingportions so that a large frictional resistance does not occur. When thetorsion angle of the torsional vibrations is within the torsion anglerange of the second rotating-direction space of the second frictionalresistance generating portion, the second rotating-direction space onlypermits the operation of the first frictional resistance suppressingportion to generate a frictional resistance of an intermediatemagnitude. When the torsion angle of the torsional vibrations exceedsthe torsion angle range of the second rotating-direction space, thesecond frictional resistance generating portion operates to generate thelargest frictional resistance.

As described above, the first frictional resistance generating portiongenerates frictional resistance of an intermediate magnitude in thetorsion angle range of the second rotating-direction engagement portionbefore the second frictional resistance generating portion operates togenerate the large frictional resistance. In this manner, the largefrictional resistance rises in a multi-step or stepwise fashion so thata wall of a high hysteresis torque does not exist when the largefrictional resistance is generated. Thereby, hitting or tapping noisesof claws, which may occur when a high hysteresis torque occurs, can bereduced in the frictional resistance generating mechanism.

According to an eighth aspect of the present invention, a frictionalresistance generating mechanism is arranged between two relativelyrotatable members of a rotary mechanism to generate a frictionalresistance in response to relative rotation that occurs between the twomembers by torsional vibrations to damp the torsional vibrations. Thefrictional resistance generating mechanism includes a first frictionalresistance generating portion and a second frictional resistancegenerating portion. The first frictional resistance generating portiondoes not operate within a first torsion angle range, and operates insecond torsion angle ranges provided on the opposite sides of the firsttorsion angle range, respectively. The second frictional resistancegenerating portion does not operate within the first and second torsionangle ranges, and operates on the opposite sides of the second torsionangle ranges.

In the frictional resistance generating mechanism, when the torsionangle of the torsional vibrations is within the first torsion anglerange, neither of the first and second frictional resistance generatingportions operates, thus, a large frictional resistance does not occur.When the torsion angle of the torsional vibrations is within the secondtorsion angle range, only the first frictional resistance generatingportion operates to generate a frictional resistance of an intermediatemagnitude. When the torsion angle of the torsional vibrations exceedsthe second torsion angle range, the second frictional resistancegenerating portion operates to generate the largest frictionalresistance.

As described above, the first frictional resistance generating portiongenerates the frictional resistance of an intermediate magnitude withinthe second torsion angle range before the second frictional resistancegenerating portion operates to generate the large frictional resistance.In this manner, the large frictional resistance rises in a multi-step orstepwise fashion so that a wall of a high hysteresis torque does notexist when the large frictional resistance is generated. Thereby,hitting or tapping noises of claws, which may occur when a highhysteresis torque occurs, can be reduced in the frictional resistancegenerating mechanism.

According to a ninth aspect of the present invention, a frictionalresistance generating mechanism is arranged between two relativelyrotatable members of a rotary mechanism to generate a frictionalresistance in response to relative rotation that occurs between the twomembers by torsional vibrations to damp the torsional vibrations. Thefrictional resistance generating mechanism includes a large frictionalresistance generating mechanism, a large frictional resistancegeneration suppressing mechanism, and a small frictional resistancegenerating mechanism. The large frictional resistance generationsuppressing mechanism has a rotating-direction space to preventoperation of the large frictional resistance generating mechanism. Thesmall frictional resistance generating mechanism generates a frictionalresistance smaller than the frictional resistance generated by the largefrictional resistance generating mechanism on the opposite sides of therotating-direction space.

In the frictional resistance generating mechanism, when the torsionangle is within the torsion angle range of a middle portion of therotating-direction space, neither of the small and large frictionalresistance generating mechanisms operates, thus, a large frictionalresistance does not occur. When the torsion angle of the torsionalvibrations is within the torsion angle range of the opposite ends of therotating-direction space, only the small frictional resistancegenerating mechanism operates to generate a frictional resistance of anintermediate magnitude. When the torsion angle of the torsionalvibrations exceeds the the torsion angle range of the rotating-directionspace, the large frictional resistance generating mechanism operates togenerate the largest frictional resistance.

As described above, the small frictional resistance generating mechanismgenerates the frictional resistance of an intermediate magnitude on theopposite ends of the torsion angle range of the rotating-direction spacebefore the large frictional resistance generating mechanism operates togenerate the large frictional resistance. In this manner, the largefrictional resistance rises in a multi-step or stepwise fashion so thata wall of a high hysteresis torque does not exist when the largefrictional resistance is generated. Thereby, hitting or tapping noisesof claws, which may occur when a high hysteresis torque occurs, can bereduced in the frictional resistance generating mechanism.

According to a tenth aspect of the present mechanism, a frictionalresistance generating mechanism is arranged between two relativelyrotatable members of a rotary mechanism to generate a frictionalresistance in response to relative rotation that occurs between the twomembers by torsional vibrations to damp the torsional vibrations. Thefrictional resistance generating mechanism includes a first frictionportion and a second friction portion. The first friction portion has afirst hysteresis torque generating portion, and a firstrotating-direction space arranged to operate in series with respect tothe first hysteresis torque generating portion in a rotating direction.The second friction portion has a second hysteresis torque generatingportion and a second rotating-direction space. The second hysteresistorque generating portion is arranged in the rotating direction betweenthe first hysteresis torque generating portion and the firstrotating-direction space. The second hysteresis torque generatingportion generates a hysteresis torque smaller than the hysteresis torquegenerated by the first hysteresis torque generating portion. The secondrotating-direction space is arranged to operate in series with respectto the second hysteresis torque generating portion in the rotatingdirection.

In the frictional resistance generating mechanism, when the torsionangle of the torsional vibrations is within the torsion angle range ofthe first rotating-direction space of the first friction portion,neither of the first and second hysteresis torque generating portionsoperates, thus, a large frictional resistance does not occur. When thetorsion angle of the torsional vibrations exceeds the torsion anglerange of the first rotating-direction space of the first frictionportion to fall within a torsion angle range of the secondrotating-direction space of the second friction portion, the secondhysteresis torque generating portion operates to generate a hysteresistorque of an intermediate magnitude. When the torsion angle of thetorsional vibrations exceeds a torsion angle range of the secondrotating-direction space, the first hysteresis torque generating portionoperates to generate the largest frictional resistance.

As described above, the second hysteresis torque generating portiongenerates the frictional resistance of an intermediate magnitude in thetorsion angle ranges of the second rotating-direction on the oppositesides of the first rotating-direction space before the first hysteresistorque generating portion operates to generate the large frictionalresistance. In this manner, the large frictional resistance rises in amulti-step or stepwise fashion so that a wall of a high hysteresistorque does not exist when the large frictional resistance is generated.Thereby, hitting or tapping noises of claws, which may occur when a highhysteresis torque occurs, can be reduced in the frictional resistancegenerating mechanism.

According to an eleventh aspect of the present invention, a frictionalresistance generating mechanism is arranged between two relativelyrotatable members of a rotary mechanism for generating a frictionalresistance in response to relative rotation that occurs between the twomembers by torsional vibrations to damp the torsional vibrations. Thefrictional resistance generating mechanism includes a first frictiongenerating portion, a second friction generating portion, a firstrotating-direction space forming portion, and a secondrotating-direction space forming portion. The second friction generatingportion is arranged to operate in parallel with the first frictiongenerating portion in the rotating direction. The firstrotating-direction space forming portion prevents the operation of thefirst friction generating portion in an initial stage of a torsionangle. The second rotating-direction space forming portion prevents theoperation of the second friction generating portion up to apredetermined torsion angle when the first friction generating portionis operating.

In the frictional resistance generating mechanism, when relativerotation starts between the two members, the first rotating-directionspace forming portion initially prevents operation of both the first andsecond friction generating portions. When the torsion angle exceeds aninitial stage, the first friction generating portion starts theoperation to generate a predetermined frictional resistance. When apredetermined torsion angle is achieved, the second rotating-directionspace forming portion is closed, and the second friction generatingportion generates a predetermined frictional resistance. Thus, the firstand second friction generating portions operate in parallel in therotating-direction to generate a frictional resistance larger than thatgenerated only by the first friction generating portion.

As described above, only the first friction generating portion operatesto generate the frictional resistance of an intermediate magnitude inthe predetermined torsion angle range of the second rotating-directionspace forming portion before the first and second friction generatingportions operate in parallel in the rotating direction to generate thelarge frictional resistance. In this manner, the large frictionalresistance rises in a multi-step or stepwise fashion so that a wall of ahigh hysteresis torque does not exist when the large frictionalresistance is generated. Thereby, hitting or tapping noises of claws,which may occur when a high hysteresis torque occurs, can be reduced inthe frictional resistance generating mechanism.

According to a twelfth aspect of the present invention, a frictionalresistance generating mechanism is arranged between two relativelyrotatable members of a rotary mechanism for generating a frictionalresistance in response to relative rotation that occurs between the twomembers by torsional vibrations to damp the torsional vibrations. Thefrictional resistance generating mechanism includes first, second, andthird friction generating portions as well as first, second, and thirdrotating-direction space forming portions. The first, second, and thirdfriction generating portions are arranged to operate in parallel witheach other in a rotating direction between the first and second rotarymembers. The first rotating-direction space forming portion prevents anoperation of the first friction generating portion in an initial stageof a torsion angle. The second rotating-direction space forming portionprevents the operation of the second friction generating portion up to apredetermined torsion angle when the first friction generating portionoperates. The third rotating-direction space forming portion prevents anoperation of the third friction generating portion until a predeterminedtorsion angle is achieved during the operation of the second frictiongenerating portion.

In the frictional resistance generating mechanism, when relativerotation starts between the two members, the first rotating directionspace forming portion initially prevents the operations of all thefirst, second, and third friction generating portions. When the torsionangle exceeds an initial stage, the first friction generating portionstarts the operation to generate a predetermined frictional resistance.When a predetermined torsion angle is achieved, the secondrotating-direction space forming portion is closed, and the secondfriction generating portion generates a predetermined frictionalresistance. Thus, the first and second friction generating portionsoperate in parallel in the rotating-direction to generate a frictionalresistance larger than that generated only by the first frictiongenerating portion. When another predetermined torsion angle isachieved, the third rotating-direction space forming portion is closed,and the third friction generating portion generates a predeterminedfrictional resistance. Thus, the first, second, and third frictiongenerating portions operate in parallel in the rotating-direction togenerate a frictional resistance larger than that generated by the firstand second friction generating portions.

As described above, only the first friction generating portion initiallyoperates before the first, second, and third friction generatingportions operate in parallel in the rotating direction to generate thelarge frictional resistance. Then, only the first and second frictiongenerating portions operate so that a frictional resistance of anintermediate magnitude is generated in a stepwise fashion. In thismanner, the large frictional resistance rises in a multi-step orstepwise fashion so that a wall of a high hysteresis torque does notexist when the large frictional resistance is generated. Thereby,hitting or tapping noises of claws, which may occur when a highhysteresis torque occurs, can be reduced in the frictional resistancegenerating mechanism.

According to a thirteenth aspect of the present invention, a frictionalresistance generating mechanism is arranged between two relativelyrotatable members of a rotary mechanism for generating a frictionalresistance in response to relative rotation that occurs between the twomembers by torsional vibrations to damp the torsional vibrations. Thefrictional resistance generating mechanism includes a plurality offriction generating portions and a plurality of rotating-direction spaceforming portions. The plurality of friction generating portions isarranged between the first and second rotary members to operate inparallel with each other in the rotating direction. The plurality ofrotating-direction space forming portions delays the operations of theplurality of friction portions to start successively the operations ofthe respective friction portions.

In the frictional resistance generating mechanism, when relativerotation occurs between the two members, the plurality ofrotating-direction space forming portions successively starts theoperations of the plurality of friction portions. Thus, the number ofthe friction generating portions operating in parallel with each otherin the rotating direction increases stepwise. In this manner, the largefrictional resistance rises in a multi-step or stepwise fashion so thata wall of a high hysteresis torque does not exist when the largefrictional resistance is generated. Thereby, hitting or tapping noisesof claws, which may occur when a high hysteresis torque occurs, can bereduced in the frictional resistance generating mechanism.

According to a fourteenth aspect of the present invention, a frictionalresistance generating mechanism is arranged between two relativelyrotatable members of a rotary mechanism for generating a frictionalresistance in response to relative rotation that occurs between the twomembers by torsional vibrations to damp the torsional vibrations. Thefrictional resistance generating mechanism includes a large frictiongenerating portion and an intermediate friction generating portion. Theintermediate friction generating portion generates an intermediatefrictional resistance smaller than a frictional resistance generated bythe large frictional resistance generating portion just before the largefriction generating portion starts operating. The magnitude of theintermediate frictional resistance may be constant, may change in amulti-step fashion or may change gradually.

In the frictional resistance generating mechanism, when relativerotation occurs between the two members, the large friction generatingportion operates to generate a large frictional resistance immediatelyafter the intermediate friction generating portion operates to generatethe intermediate frictional resistance. In this manner, the largefrictional resistance rises in a multi-step or stepwise fashion so thata wall of a high hysteresis torque does not exist when the largefrictional resistance is generated. Thereby, hitting or tapping noisesof claws, which may occur when a high hysteresis torque occurs, can bereduced in the frictional resistance generating mechanism.

According to a fifteenth aspect of the present invention, a flywheelassembly to transmit a torque from a crankshaft of an engine includes aflywheel, an elastic coupling mechanism and a plate-like couplingportion. The flywheel has a friction surface. The elastic couplingmechanism is a mechanism to couple elastically the flywheel and thecrankshaft in a rotational direction. The elastic coupling mechanism hasa pair of first disk-shaped members, a second disk-shaped member, and anelastic member. The first disk-shaped members are axially spaced fromeach other and fixed together. The second disk-shaped member is arrangedbetween the pair of first disk-shaped members. The elastic member isprovided to couple elastically the pair of first disk-shaped members tothe second disk-shaped member in the rotational direction. Theplate-like coupling portion extends between outer peripheries of thepair of first disk-shaped members and couples the pair of firstdisk-shaped members together.

In this flywheel assembly, the plurality of elastic members transmitsthe torque between the first disk-shaped plate pair and the seconddisk-shaped plate. When relative rotation occurs between the pair offirst disk-shaped plate pair and the second disk-shaped plate, theelastic members are compressed therebetween. A conventional stop pin iseliminated, and the plate-like coupling portion couples the firstdisk-shaped plate pair to the second disk-shaped plate. The plate-likecoupling portion is radially shorter than the conventional stop pin,therefore can be disposed in the radially outermost position of thesecond disk-shaped plate. Therefore, the plate-like coupling portiondoes not interfere with the elastic members so that a torsion angle of adamper mechanism can be sufficiently increased.

According to a sixteenth aspect of the present invention, the flywheelassembly of the fifteenth aspect further has a feature such that theplate-like coupling portions are arranged at a plurality ofcircumferentially shifted positions, respectively.

According to a seventeenth aspect of the present invention, the flywheelassembly of the fifteenth or sixteenth aspect further has a feature suchthat the plate-like coupling portion has main surfaces directed radiallyinward and outward, respectively.

According to an eighteenth aspect of the present invention, the flywheelassembly of the fifteenth, sixteenth or seventeenth aspect further has afeature such that the plate-like coupling portion extends integrallyfrom one of the pair of first disk-shaped members.

According to nineteenth aspect of the present invention, the flywheelassembly of any one of the fifteenth to eighteenth aspects further has afeature such that the second disk-shaped member is provided with a stopportion colliding in the rotational direction with the disk-shapedmember when a torsion angle between the first disk-shaped member pairand the second disk-shaped member increases.

According to a twentieth aspect of the present invention, a frictionalresistance generating mechanism is arranged between two relativelyrotatable members of a rotary mechanism to generate a frictionalresistance in response to relative rotation that occurs between the twomembers by torsional vibrations to damp the torsional vibrations. Thefrictional resistance generating mechanism includes a first rotarymember, a second rotary member, a first intermediate member, and asecond intermediate member. The second rotary member is rotatablerelatively to the first rotary member. The first intermediate memberengages with the first rotary member via a first rotating-directionspace. The second intermediate member cooperates with the firstintermediate member to form an engagement portion engaging with thefirst intermediate member via a second rotating-direction space. Thesecond intermediate member also cooperates with the first intermediatemember to form a first frictional resistance generating portion slidablyand frictionally engaging in the rotating direction with the firstintermediate member. Further, the second intermediate member cooperateswith the second rotary member to form a second frictional resistancegenerating portion slidably and frictionally engaging in the rotatingdirection with the second rotary member to generate a frictionalresistance larger than a frictional resistance generated by the firstfrictional resistance generating portion.

In this frictional resistance generating mechanism, when the firstrotary member rotates relatively to the second rotary member, the firstrotating-direction space between the first rotary member and the firstintermediate member initially decreases. In this operation, neither thefirst nor the second frictional resistance generating portions generatesa frictional resistance. When the first rotating-direction spacedisappears, the first intermediate member rotates together with thefirst rotary member, and rotates relatively to the second intermediatemember. In this relative rotation, the first frictional resistancegenerating portion generates a frictional resistance, and at the sametime, the second rotating-direction space decreases. When the secondrotating-direction space disappears, the second intermediate memberrotates together with the first intermediate member, and rotatesrelatively to the second rotary member. In this relative rotation, thesecond frictional resistance generating portion generates a frictionalresistance larger than that generated by the first frictional resistancegenerating portion.

Consequently, in the frictional resistance generating mechanism, when atorsion angle of torsional vibrations is in an angle range of the firstrotating-direction space, the first rotating-direction space preventsthe operation of the first and second frictional resistance generatingportions so that a large frictional resistance does not occur. When thetorsion angle of torsional vibrations is in an angle range of the secondrotating-direction space, due to the second rotating-direction spaceonly the first frictional resistance generating portion operates so thata frictional resistance of an intermediate magnitude occurs. When thetorsion angle of torsional vibrations exceeds the angle range of thesecond rotating-direction space, the second frictional resistancegenerating portion operates to generate the largest frictionalresistance.

As described above, the first frictional resistance generating portiongenerates the frictional resistance of an intermediate magnitude in thetorsion angle range of the second rotating-direction space before thesecond frictional resistance generating portion operates to generate thelarge frictional resistance. In this manner, the large frictionalresistance rises in a multi-step or stepwise fashion so that a wall of ahigh hysteresis torque does not exist when generating the largefrictional resistance. Thereby, hitting or tapping noises of claws,which may occur when a high hysteresis torque occurs, can be reduced inthe frictional resistance generating mechanism.

According to a twenty-first aspect of the present invention, thefrictional resistance generating mechanism of the twentieth aspectfurther has a feature such that the first rotating-direction space islarger than the second rotating-direction space.

According to a twenty-second aspect of the present invention, thefrictional resistance generating mechanism of the twentieth ortwenty-first aspect further has a feature such that the first and secondintermediate members are disk-shaped members axially overlapping andbeing in contact with each other.

According to a twenty-third aspect of the present invention, thefrictional resistance generating mechanism of the twenty-second aspectfurther has a feature such that the second intermediate member is formedof a pair of members each being in contact with one of axially oppositesides of the first intermediate member. Each of the pair of memberscooperates with the first intermediate member to form the firstfrictional resistance generating portion therebetween, and cooperateswith the second rotary member to form the second frictional resistancegenerating portion therebetween.

According to a twenty-fourth aspect of the present invention, thefrictional resistance generating mechanism of the twenty-second ortwenty-third aspect further has a feature such that the firstrotating-direction space is radially positioned in an area defined byaxially overlapping portions of the first and second intermediatemembers.

In this frictional resistance generating mechanism, the radial positionof the first rotating-direction space is not shifted radially outwardfrom the axially overlapping portions of the first and secondintermediate members so that the structure can be small in size.

According to a twenty-fifth aspect of the present invention, thefrictional resistance generating mechanism of the twenty-fourth aspectfurther has a feature such that the first rotary member has adisk-shaped portion axially overlapping the first intermediate member.The first rotating-direction space is formed between the firstintermediate member and the disk-shaped portion of the first rotarymember.

In this frictional resistance generating mechanism, the firstrotating-direction space is formed between the first intermediate memberand the disk-shaped portion of the first rotary member so that thestructure of the first rotating-direction space can be simple.Therefore, the accuracy of the first rotating-direction space isimproved.

According to a twenty-sixth aspect of the present invention, thefrictional resistance generating mechanism of the twenty-fifth aspectfurther has a feature such that one of the first intermediate member andthe disk-shaped portion of the first rotary member is provided with aspace extending in the rotating direction, and the other is providedwith a projected portion extending axially through the space to form thefirst rotating-direction space.

In this frictional resistance generating mechanism, since the firstintermediate member and the disk-shaped portion of the first rotarymember are provided with the space and the projection, the structure ofthe first rotating-direction space can be simple. Therefore, theaccuracy of the first rotating-direction space is improved.

According to a twenty-seventh aspect of the present invention, thefrictional resistance generating mechanism of the twenty-sixth aspectfurther has a feature such that the space is formed in the disk-shapedportion of the first rotary member. The first intermediate member isformed of a pair of members arranged on axially opposite sides of thedisk-shaped portion, respectively. One of the pair of members has theprojected portion, and is unrotatably engaged with the other of the pairof members via the projected portion.

According to a twenty-eighth aspect of the present invention, africtional resistance generating mechanism is arranged between tworelatively rotatable members of a rotary mechanism to generate africtional resistance in response to relative rotation that occursbetween the two members by torsional vibrations to damp the torsionalvibrations. The frictional resistance generating mechanism includes afirst rotary member, a second rotary member, a first intermediatemember, and a second intermediate member. The second rotary member isrotatable relatively to the first rotary member. The first intermediatemember engages with the first rotary member via a first space in therotating-direction, and cooperates with the second rotary member to forma first friction generating portion therebetween. The secondintermediate member is arranged between the first and second rotarymembers to operate with respect to the first intermediate member in arotating direction such that an end of the second intermediate memberand an end of the first intermediate member exert forces on each other,engages with the first intermediate member via a second space in therotating-direction, and cooperates with the second rotary member to forma second friction generating portion therebetween.

In this frictional resistance generating mechanism, when the firstrotary member rotates relatively to the second rotary member, the firstrotating-direction space between the first rotary member and the firstintermediate member initially decreases. In this operation, neither thefirst nor the second friction generating portions generates a frictionalresistance. When the first rotating-direction space disappears, thefirst intermediate member rotates together with the first rotary member,and rotates relatively to the second intermediate member. In thisrelative rotation, the first friction generating portion generates africtional resistance, and at the same time, the secondrotating-direction space decreases. When the second rotating-directionspace disappears, the second intermediate member rotates together withthe first intermediate member, and rotates relatively to the secondrotary member. In this relative rotation, the first and second frictiongenerating portions operate in parallel in the rotating direction, andgenerate a frictional resistance larger than that generated only by thefirst friction generating portion.

In this manner, the large frictional resistance rises in a multi-step orstepwise fashion so that a wall of a high hysteresis torque does notexist when generating the large frictional resistance. Thereby, hittingor tapping noises of claws, which may occur when a high hysteresistorque occurs, can be reduced in the frictional resistance generatingmechanism.

According to a twenty-ninth aspect of the present invention, thefrictional resistance generating mechanism of the ninth aspect furtherhas a feature such that the frictional resistance generating mechanismfurther includes a third intermediate member arranged between the firstand second rotary members to operate with respect to the first andsecond intermediate members in the rotating direction such that an endof the third intermediate member and an end of the first and secondintermediate members exert forces on each other, engaging with thesecond intermediate member via a third rotating-direction space, andcooperating with the second rotary member to form a third frictiongenerating portion.

In this frictional resistance generating mechanism, when the firstrotary member rotates relatively to the second rotary member, the firstrotating-direction space between the first rotary member and the firstintermediate member initially decreases. In this operation, neither thefirst nor the second friction generating portions generates a frictionalresistance. When the first rotating-direction space is closed, the firstintermediate member rotates together with the first rotary member, androtates relatively to the second intermediate member. In this relativerotation, the first friction generating portion generates a frictionalresistance, and at the same time, the second rotating-direction spacedecreases. When the second rotating-direction space disappears, thesecond intermediate member rotates together with the first intermediatemember, and rotates relatively to the second rotary member. In thisrelative rotation, the first and second friction generating portionsoperate in parallel in the rotating direction, and generate a frictionalresistance larger than that generated only by the first frictiongenerating portion. When the third rotating-direction space disappears,the third intermediate member rotates together with the secondintermediate member, and rotates relatively to the second rotary member.In this relative rotation, the first, second, and third frictiongenerating portions operate in parallel in the rotating direction, andgenerate a frictional resistance larger than that generated only by thefirst and second friction generating portions.

In this manner, the large frictional resistance rises in a multi-step orstepwise fashion so that hitting or tapping noises of claws, which mayoccur when a high hysteresis torque occurs, can be reduced in thefrictional resistance generating mechanism.

According to a thirtieth aspect of the present invention, a frictionalresistance generating mechanism is arranged between two relativelyrotatable members of a rotary mechanism to generate a frictionalresistance in response to relative rotation that occurs between the twomembers by torsional vibrations to damp the torsional vibrations. Thefrictional generating mechanism includes a first rotary member, a secondrotary member, and a plurality of friction members. The second rotarymember is rotatable relatively to the first rotary member. The pluralityof friction members is arranged in a rotating direction between thefirst and second rotary members, and each of the friction membersfrictionally engages with the second rotary member. The friction membersengage in series with each other in the rotating direction via arotating-direction space such that an end of one exerts force on an endof the other.

In this frictional resistance generating mechanism, when the firstrotary member rotates relatively to the second rotary member, theplurality of friction members are driven by the first rotary member toslide with respect to the second rotary member and to generate africtional resistance. In this operation, the respective frictionmembers are successively driven while being spaced from each other bythe rotating-direction spaces. Thus, the hysteresis torque increases ina stepwise fashion.

In this manner, the large frictional resistance rises in a multi-step orstepwise fashion so that a wall of a high hysteresis torque does notexist when generating the large frictional resistance. Thereby, hittingor tapping noises of claws, which may occur when a high hysteresistorque occurs, can be reduced in the frictional resistance generatingmechanism.

According to the frictional resistance generating mechanism of theinvention, when a torsion angle of torsional vibrations is in an anglerange of the first rotating-direction space, the firstrotating-direction space prevents the operation of the first and secondfrictional resistance generating portions so that a large frictionalresistance does not occur. When the torsion angle of torsionalvibrations is in an angle range of the second rotating-direction space,the second rotating-direction space operates only the first frictionalresistance generating portion so that a frictional resistance of anintermediate magnitude occurs. When the torsion angle of torsionalvibrations exceeds the angle range of the second rotating-directionspace, the second frictional resistance generating portion operates togenerate the largest frictional resistance.

As described above, the first frictional resistance generating portiongenerates the frictional resistance of an intermediate magnitude in thetorsion angle range of the second rotating-direction space before thesecond frictional resistance generating portion operates to generate thelarge frictional resistance. In this manner, the large frictionalresistance rises in a multi-step or stepwise fashion so that a wall of ahigh hysteresis torque does not exist when generating the largefrictional resistance. Thereby, hitting or tapping noises of claws,which may occur when a high hysteresis torque occurs, can be reduced inthe frictional resistance generating mechanism.

These and other objects, features, aspects, and advantages of thepresent invention will become apparent to those skilled in the art fromthe following detailed description, which, taken in conjunction with theannexed drawings, discloses a preferred embodiment of the presentinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring now to the attached drawings which form a part of thisoriginal disclosure:

FIG. 1 is a schematic cross-sectional view of a clutch device inaccordance with a preferred embodiment of the present invention;

FIG. 2 is an alternate schematic cross-sectional view of the clutchdevice;

FIG. 3 is an elevational view of a flywheel damper of the clutch device;

FIG. 4 is a fragmentary view showing, on an enlarged scale, a structureof the clutch device of FIG. 1, and particularly illustrating a platecoupling portion thereof;

FIG. 5 is a fragmentary view showing, on an enlarged scale, a structureof the clutch device of FIG. 1, and particularly illustrating africtional resistance generating mechanism thereof;

FIG. 6 is a fragmentary view showing, on an enlarged scale, a structureof the clutch device of FIG. 2, and particularly illustrating analternate view of the frictional resistance generating mechanism;

FIG. 7 is a rear elevational view of the flywheel damper, illustratingthe frictional resistance generating mechanism;

FIG. 8 is an elevational view of a damper mechanism in a hub flange ofthe clutch device:

FIG. 9 is an elevational view of the damper mechanism in clutch andretaining plates of the clutch device;

FIG. 10 is an elevational view of a second spring seat of the dampermechanism;

FIG. 11 is a side view of the second spring seat viewed in a directionof arrow XI in FIG. 10;

FIG. 12 is a plan view of the second spring seat viewed in a directionof arrow XII in FIG. 10;

FIG. 13 is a rear view of the second spring seat viewed in a directionof arrow XIII in FIG. 10;

FIG. 14 is an elevational view of a first spring seat of the dampermechanism;

FIG. 15 is a side view of the first spring seat viewed in a direction ofan arrow XV in FIG. 14;

FIG. 16 is a rear view of the first spring seat viewed in a direction ofan arrow XVI in FIG. 15;

FIG. 17 is a cross-sectional view of the first spring seat taken alongline XVII—XVII in FIG. 16;

FIG. 18 is a fragmentary cross-sectional view illustrating theengagement between the second spring seat and the hub flange;

FIG. 19 is a fragmentary cross-sectional view illustrating engagement ofthe second spring seat with the clutch and retaining plates;

FIG. 20 is a view of a mechanical circuit diagram of the dampermechanism;

FIG. 21 is a view of a torsion characteristic diagram of the dampermechanism;

FIG. 22 is a fragmentary cross-sectional view illustrating an operationof a small coil spring of the damper mechanism;

FIG. 23 is a fragmentary cross-sectional view illustrating an operationof the small coil spring;

FIG. 24 is a fragmentary elevational view illustrating an operation ofthe frictional resistance generating mechanism;

FIG. 25 is a fragmentary elevational view illustrating an operation ofthe frictional resistance generating mechanism;

FIG. 26 is a fragmentary elevational view illustrating an operation ofthe frictional resistance generating mechanism;

FIG. 27 is a view of a diagram illustrating torsion characteristics ofthe damper mechanism;

FIG. 28 is a view of a diagram illustrating torsion characteristics ofthe damper mechanism;

FIG. 29 is a view of a diagram illustrating torsion characteristics ofthe damper mechanism;

FIG. 30 is a cross-sectional view illustrating a frictional resistancegenerating mechanism in accordance with a second preferred embodiment ofthe present invention;

FIG. 31 is an alternate cross-sectional view illustrating the frictionalresistance generating mechanism of the second embodiment.

FIG. 32 is an elevational view a first high-friction-coefficientfriction washer of the frictional resistance generating mechanism of thesecond embodiment;

FIG. 33 is a rear elevational view of the firsthigh-friction-coefficient friction washer of the second embodiment;

FIG. 34 is an elevational view of a second high-friction-coefficientfriction washer of the frictional resistance generating mechanism of thesecond embodiment;

FIG. 35 is a rear fragmentary elevational view of the secondhigh-friction-coefficient friction washer of the second embodiment;

FIG. 36 is an elevational view of an input friction plate of thefrictional resistance generating mechanism of the second embodiment;

FIG. 37 is an elevational view of a bushing of the frictional resistancegenerating mechanism of the second embodiment;

FIG. 38 is an elevational view of a first low-friction-coefficientfriction washer of the frictional resistance generating mechanism of thesecond embodiment;

FIG. 39 is a fragmentary plan view illustrating a structure of a firstrotating-direction engagement portion of the frictional resistancegenerating mechanism of the second embodiment;

FIG. 40 is a fragmentary elevational view illustrating structures of thefirst and second rotating-direction engagement portions of the secondembodiment;

FIG. 41 is a view of a mechanical circuit diagram of a damper mechanismof a clutch device in accordance with the second embodiment;

FIG. 42 is a view of a torsion characteristic diagram of the dampermechanism of the second embodiment;

FIG. 43 is a view of a torsion characteristic diagram of the dampermechanism of the second embodiment;

FIG. 44 is a view of a torsion characteristic diagram of the dampermechanism of the second embodiment;

FIG. 45 is a view of a torsion characteristic diagram of the dampermechanism of the second embodiment;

FIG. 46 is a schematic cross-sectional view of a frictional resistancegenerating mechanism in accordance with a third preferred embodiment ofthe present invention;

FIG. 47 is an alternate schematic cross-sectional view of the frictionalresistance generating mechanism of the third embodiment;

FIG. 48 is a fragmentary elevational view illustrating a firstrotating-direction engagement portion of the frictional resistancegenerating mechanism of the third embodiment;

FIG. 49 is a fragmentary elevational view illustrating a secondrotating-direction engagement portion of the frictional resistancegenerating mechanism of the third embodiment;

FIG. 50 is a schematic cross-sectional view illustrating assembly of thefrictional resistance generating mechanism of the third embodiment;

FIG. 51 is a view of a mechanical circuit diagram of a damper mechanismof a clutch device in accordance with the third embodiment;

FIG. 52 is a view of a mechanical circuit diagram of a damper mechanismin accordance with a fourth preferred embodiment of the presentinvention;

FIG. 53 is a view of a torsion characteristic diagram of a dampermechanism of the fourth embodiment;

FIG. 54 is a view of a mechanical circuit diagram of a damper mechanismin accordance with a fifth preferred embodiment of the presentinvention;

FIG. 55 is a view of a torsion characteristic diagram of the dampermechanism of the fifth embodiment;

FIG. 56 is a view of a torsion characteristic diagram of the dampermechanism in accordance with a sixth preferred embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Selected embodiments of the present invention will now be explained withreference to the drawings. It will be apparent to those skilled in theart from this disclosure that the following descriptions of theembodiments of the present invention are provided for illustration onlyand not for the purpose of limiting the invention as defined by theappended claims and their equivalents.

First Embodiment

A clutch device 1 in accordance with a preferred embodiment of thepresent invention shown in FIGS. 1 and 2 is to couple providedreleasably torque between a crankshaft 2 on an engine side and an inputshaft 3 on a transmission side. The clutch device 1 is primarily formedof a first flywheel assembly 4, a second flywheel assembly 5, a clutchcover assembly 8, a clutch disk assembly 9, and a release device 10. Thefirst and second flywheel assemblies 4 and 5 are combined to form aflywheel damper 11, which includes a damper mechanism 6 and is describedlater.

In FIGS. 1 and 2, O—O indicates a rotation axis of the clutch device 1.An engine (not shown) is disposed on the left side in FIGS. 1 and 2, anda transmission (not shown) is disposed on the right side. In followingdescription, the left side in FIGS. 1 and 2 will be referred to as theengine side, which is based on the axial direction, and the right sidewill be referred to the transmission side, which is based on the axialdirection. In FIG. 3, an arrow R1 indicates a drive side, i.e., forwardside in the rotational direction, and an arrow R2 indicates a reversedrive side (rearward side in the rotational direction).

First Flywheel Assembly

Referring to FIGS. 1 and 2, the first flywheel assembly 4 is fixed to anend of the crankshaft 2. The first flywheel assembly 4 is a member thatensures a large moment of inertia on the crankshaft side. The firstflywheel assembly 4 is primarily formed of a disk-shaped member 13, anannular member 14, and a support plate 39, which will be describedlater. The disk-shaped member 13 has a radially inner end fixed to anend of the crankshaft 2 by a plurality of bolts 15. The disk-shapedmember 13 has bolt insertion apertures 13 a located corresponding to thebolts 15, respectively. Each bolt 15 is axially attached to thecrankshaft 2 from the transmission side. The annular member 14 has arelatively thick block-like form, and is axially fixed to thetransmission side of the radially outer end of the disk-shaped member13. The radially outer end of the disk-shaped member 13 is welded to theannular member 14. Further, a ring gear 17 for an engine starter isfixed to the outer peripheral surface of the annular member 14. Thefirst flywheel assembly 4 may be integrally formed.

A structure of the radially outer portion of the disk-shaped member 13will now be described in greater detail. As shown in FIG. 5, theradially outer portion of the disk-shaped member 13 has a flat form,having a friction member 19 fixed to its axial surface on thetransmission side. The friction member 19 is formed of a plurality ofarc-shaped members, and has an annular form as a whole. In a relativerotation suppressing mechanism 24, which will be described later, thefriction member 19 functions as a member for damping shock, which iscaused when the first and second flywheel assemblies 4 and 5 are coupledtogether. The friction member 19 also serves to stop rapidly therelative rotation in the coupling operation. The friction member 19 maybe fixed to a disk-shaped plate 22, which will be described later.

The disk-shaped member 13 is provided with a cylindrical portion 20 atits outer periphery extending axially toward the transmission side asshown in FIG. 5. The cylindrical portion 20 is supported by the innerperipheral surface of the annular member 14, and is provided with aplurality of recesses 20 a at its end. Each recess 20 a has apredetermined angular length in the rotational direction. It can bedeemed that each recess 20 a is defined by axial projections on thecylindrical portion 20.

Second Flywheel Assembly

The second flywheel assembly 5 is primarily formed of a flywheel 21 witha friction surface, and the disk-shaped plate 22. The flywheel 21 withthe friction surface has an annular and disk-shaped form, and is axiallylocated on the transmission side with respect to the outer peripheralportion of the first flywheel assembly 4. The flywheel 21 with thefriction surface is provided with a first friction surface 21 a on itstransmission side. The first friction surface 21 a is an annular andflat surface, and can be connected to the clutch disk assembly 9, whichwill be described later. The flywheel 21 with the friction surface isfurther provided with a second friction surface 21 b on its engine sidein the axial direction. The second friction surface 21 b is an annularand flat surface, and functions as a frictional sliding surface of africtional resistance generating mechanism 7, which will be describedlater. As compared with the first friction surface 21 a, the secondfriction surface 21 b has a slightly smaller outer diameter and asignificantly larger inner diameter. Accordingly, the second frictionsurface 21 b has a larger effective radius than the first frictionsurface 21 a. The second friction surface 21 b is axially opposed to thefriction member 19.

Description will now be given on the disk-shaped plate 22. As seen inFIG. 2, the disk-shaped plate 22 is disposed axially between the firstflywheel assembly 4 and the flywheel 21 having the friction surface. Thedisk-shaped plate 22 has a radially outer portion fixed to a radiallyouter portion of the flywheel 21 having the friction surface by aplurality of rivets 23, and functions as a member rotational togetherwith the flywheel 21 having the friction surface. More specifically, asseen in FIG. 5, the disk-shaped plate 22 is formed of a radially outerfixing portion 25, a radially outer cylindrical portion 26, a contactportion 27, and a radially inner cylindrical portion 28, which arealigned radially in this order. The radially outer fixed portion 25 isflat and is in axial contact with the surface on the engine side of theradially outer portion of the flywheel 21 having the friction surface.The radially outer fixing portion 25 is fixed to the radially outerportion of the flywheel 21 by the rivets 23 already described. Thecylindrical portion 26 extends axially toward the engine from the innerperiphery of the radially outer fixed portion 25. The cylindricalportion 26 is located radially inside the cylindrical portion 20 of thedisk-shaped member 13. The cylindrical portion 26 is provided with aplurality of recesses 26 a. Each recess 26 a is formed corresponding tothe recess 20 a in the cylindrical portion 20 of the disk shaped member13. The contact portion 27 has a circular and flat form, and correspondsto the friction member 19. The contact portion 27 is axially opposed tothe second friction surface 21 b of the flywheel 21 having the frictionsurface with a space therebetween. Various members of the frictionalresistance generating mechanism 7 to be described later are arranged inthis space. The frictional resistance generating mechanism 7 is disposedbetween the contact portion 27 of the disk-shaped plate 22 of the secondflywheel assembly 5 and the flywheel 21 having the friction surface sothat the required space of the structure can be small. The radiallyinner cylindrical portion 28 extends axially toward the transmission,and has an end neighboring the flywheel 21 having the friction surface.The radially inner cylindrical portion 28 is provided with an outerperipheral surface 28 a at its base portion, which is larger in diameterthan an outer peripheral surface 28 b on its tip end portion, and astepped portion is formed between these surfaces 28 a and 28 b.

As seen in FIGS. 1 and 2, the support plate 39 of the first flywheelassembly 4 is a member to support radially the second flywheel assembly5 with respect to the first flywheel assembly 4. The support plate 39 isformed of a disk-shaped portion 39 a and a cylindrical portion 39 bextending axially from its inner periphery toward the transmission. Thedisk-shaped portion 39 a is disposed axially between the end surface ofthe crankshaft 2 and the disk-shaped member 13. The disk-shaped portion39 a is provided with bolt insertion apertures 39 c corresponding to thebolt insertion apertures 13 a, respectively. Owing to the abovestructure, the support plate 39 is fixed to the crankshaft 2 by thebolts 15 together with the disk-shaped member 13 and an inputdisk-shaped plate 32.

An inner peripheral surface of the flywheel 21 with the friction surfaceis supported by the outer peripheral surface of the cylindrical portion39 b of the support plate 39 via a bushing 47. In this manner, thesupport plate 39 centers the flywheel 21 having the friction surfacewith respect to the first flywheel assembly 4 and the crankshaft 2.

Damper Mechanism

Description will now be given on the damper mechanism 6. The dampermechanism 6 is a mechanism to couple elastically the crankshaft 2 withthe flywheel 21 having the friction surface in the rotational direction.The damper mechanism 6 is formed of a high-rigidity damper 38, whichincludes a plurality of coil springs 33, and the frictional resistancegenerating mechanism 7. The damper mechanism 6 further includes alow-rigidity damper 37 for exhibiting low-rigidity characteristics in aregion of a small torsion angle. Further, as shown in FIG. 20, the low-and high-rigidity dampers 37 and 38 are disposed to operate in series inthe rotational direction, and to operate in parallel with the frictionalresistance generating mechanism 7 in the rotational direction in thetorque transmission system.

Referring again to FIGS. 1 and 2, a pair of output disk-shaped plates(30 and 31) is formed of a first plate 30 axially arranged on the engineside and a second plate 31 axially arranged on the transmission side.These plates 30 and 31 have disk-shaped forms respectively, and areaxially spaced by a predetermined distance from each other. Each ofplates 30 and 31 is provided with a plurality of spaced windows 30 a or31 a in the circumferential direction. The windows 30 a and 31 a areconfigured to support the coil springs 33, which will be describedlater, in the axial and rotational directions. Each window 30 a and 31 ahas a cut and bent portion, which axially holds the coil spring 33 andis in contact with circumferentially opposite ends thereof. As shown inFIG. 9, each of the windows 30 a and 31 a is defined by a pair of endsurfaces 94, which are located on the opposite ends in the rotationaldirection respectively, as well as a radially outer support portion 95and a radially inner support portion 96. Each end surface 94 and theradially inner support portion 96 extend substantially straight in theradial direction and the tangential direction respectively. The radiallyouter support portion 95 extends along an arc in the rotationaldirection.

A structure of the second plate 31 will now be described in greaterdetail with reference to FIGS. 1 and 2. A disk-shaped body of the secondplate 31 is provided with four circumferentially spaced windows 31 a,and is also provided with rivet apertures 69 for rivets 68, each ofwhich is located between circumferentially neighboring windows 31 a, aswill be described later. As shown in FIGS. 3 and 4, the disk-shaped bodyof the second plate 31 is provided with a plurality of plate couplingportions 40 at its outer periphery extending axially toward the engine,i.e., toward the first plate 30. The plate coupling portion 40 is formedof an axially extending portion 41 and a fixed portion 42 extendingradially inward from the end of the extending portion 41. The end of theextending portion 41 is substantially located radially outside orparallel to the first plate 30. The extending portion 41 has mainsurfaces directed radially inward and outward respectively, and thus hasa radial width equal to the thickness of the plate 31. The fixed portion42 is in contact with the side surface of the first plate 30 on theaxial transmission side, and is fixed thereto by rivets 68. In thismanner, the plates 30 and 31 are fixed together for rotation together,and an intended axial space is maintained therebetween.

The input disk-shaped plate 32 is a disk-shaped member, disposed betweenthe plates 30 and 31. The input disk-shaped plate 32 has a plurality ofwindow apertures 32 a each extending in the circumferential direction,and the coil spring 33 and a small coil spring 45 are arranged withinthe window aperture 32 a. As shown in FIG. 8, the window aperture 32 ais formed of a pair of end surfaces 91, which are located on theopposite ends in the rotational direction, respectively, as well as aradially outer support portion 92 and a radially inner support portion93. Each end surface 91 extends substantially straight in the radialdirection. Each of the radially outer support portion 92 and theradially inner support portion 93 extends along an arc in the rotationaldirection. The input disk-shaped plate 32 is provided with recesses 32b, each of which is located circumferentially between the neighboringwindow apertures 32 a to allow the rivet 68 to pass axiallytherethrough, as will be described later. As shown in FIGS. 3 and 4, theinput disk-shaped plate 32 is provided with contact portions 32 c, eachof which is spaced in the rotational direction from the extendingportion 41 but can come into contact with the extending portion 41.According to the above structure, the plate coupling portions 40 and thecontact portions 32 c form a stop mechanism in the damper mechanism 6 ofthis embodiment. However, the stop mechanism may be formed of portionsother than the above.

Each coil spring 33 is formed of a combination of large and smallsprings. Each coil spring 33 is arranged within the corresponding windowaperture 32 a and windows 30 a and 31 a, and is supported at itsopposite sides in the radial direction as well as at its opposite sidesin the rotational direction. Each coil spring 33 is also supported atits opposite sides in the axial direction within the windows 30 a and 31a.

Then, description will be given on a coupling structure 34 to couple theoutput disk-shaped plates 30 and 31 with the flywheel 21 having thefriction surface. The coupling structure 34 is formed of bolts 35 andnuts 36. The second plate 31 is provided with a plurality of fixedportions 31 b at its inner periphery, which are partially cut andshifted axially toward the transmission, as shown in FIGS. 3 and 4. Adisk-shaped body of the second plate 31 is slightly spaced from thesurface on the axially engine side of the flywheel 21 having thefriction surface, however the fixed portions 31 b are in contact withthe surface on the axially engine side of the flywheel 21 having thefriction surface. The bolt 35 projecting axially toward the transmissionis welded to each fixed portion 31 b. The flywheel 21 with the frictionsurface is provided with concavities 21 c and apertures 21 d atpositions corresponding to the fixed portions 31 b and the bolts 35. Theconcavities 21 c are formed at the surface on the axially transmissionside of the flywheel 21 with the friction surface, and the apertures 21d coaxially extend through bottom walls of the concavities 21 crespectively. The foregoing bolt 35 is axially inserted into theaperture 21 d from the axially engine side. The nut 36 is axiallylocated on the transmission side against the concavity 21 c and aperture21 d, and is engaged with the bolt 35. An end surface of the nut 36 isseated on the bottom surface of the concavity 21 c.

(1-4-2) Low-Rigidity Damper

The low-rigidity damper 37 is primarily formed of the small coil springs45. The small coil spring 45 is much smaller in free length, wirediameter, and coil diameter than the coil spring 33, and has anextremely small rigidity. As shown in FIG. 3, the small coil springs 45are arranged in two of the four window apertures 32 a, and particularlyin the diametrally opposed two window apertures 32 a (i.e., upper andlower window apertures 32 a in FIG. 3). In each window aperture 32 a,the small coil springs 45 are arranged on the opposite sides, in therotational direction, of the coil spring 33. Edges of the windowapertures 32 a and windows 30 a and 31 a support an outer end of eachsmall coil spring 45 in the rotational direction. Therefore, the smallcoil spring 45 operates in series with respect to the coil spring 33. Ineach of the diametrally opposed two windows apertures 32 a, which arelocated on the right and left sides in FIG. 3, among the four windowapertures 32 a, a space 79 of a predetermined angle is maintained in therotational direction between each end of the coil spring 33 and theneighboring end of the window aperture 32 a.

Description will now be given in greater detail. As shown in FIGS. 8 and9, a first spring seat 70 is disposed between each small coil spring 45and the corresponding coil spring 33. As shown more specifically inFIGS. 14 to 17, the first spring seat 70 is formed of a support portion81 having a disk-shaped form, a first projection 82, and a secondprojection 83. The support portion 81 has an annular first supportsurface 81 a, which comes into contact with the end surface of a largespring 33 a of the coil spring 33 in the rotational direction. The firstprojection 82 projects from the first support surface 81 a, and has anannular second support surface 82 a, which contacts with the rotationalend surface of a small spring 33 b of the coil spring 33 and a firstouter peripheral surface 82 b, which contacts with an inner peripheralsurface of the large spring 33 a. The second projection 83 projects fromthe second support surface 82 a of the first projection 82 and has aflat end surface 83 a and a second outer peripheral surface 83 b whichcontacts with the inner peripheral surface of the small spring 33 b. Thesupport portion 81 also has a second support surface 81 b on the sideopposite to the first support surface 81 a. The second support surface81 b is spaced in the rotational direction from the end surface 91 ofthe window aperture 32 a in the input disk-shaped plate 32 as shown inFIG. 8, however it is in contact with or close to the end surfaces 94 ofthe windows 30 a and 31 a in the first and second plates 30 and 31.

As seen in FIG. 17, the first spring seat 70 further has a concavity 85,which is formed at its end surface remote from the first and secondprojections 82 and 83 for inserting the small coil spring 45 therein. Asshown in FIGS. 16 and 17, the concavity 85 is primarily formed of firstand second portions 86 and 87. The first portion 86 of the concavity 85has a circular caved form when viewed in the rotational direction and isformed in a portion corresponding to the second projection 83. Thesecond portion 87 of the concavity 85 forms an external opening portionextending to the first portion 86, and has surfaces 88 and 89 whichextend from the first portion 86 and diverge toward the externalopening. Straight surfaces 88 a and 89 a are ensured between the openingand the respective surfaces 88 and 89. An end of the small coil spring45 is disposed within the concavity 85 of the first spring seat 70 asshown in FIG. 22 and an end portion thereof is inserted into the firstportion 86 of the concavity 85. The end of the first spring seat 70 isin contact with the bottom surface of the first portion 86 of theconcavity 85 allow torque transmission. The outer peripheral surface ofthe end portion of the first spring seat 70 is fitted into the firstportion of the concavity 85, and is in contact with or close to theperipheral surface thereof. In the state described above, a small radialspace is maintained between the small coil spring 45 and the radialsurface 88 on the radially inner side, and a large radial space ismaintained between the small coil spring 45 and the radial surface 89 onthe radially outer side as shown in FIG. 22.

As shown in FIGS. 10 to 13, a second spring seat 71 is formed of a body72 and a pair of engagement projections 73 and 74. The body 72substantially has a columnar form extending in the axial direction. Asshown in FIGS. 12 and 13, the body 72 has a first concavity 77 on a sidesurface of the small coil spring 45, and also has a second concavity 74on the opposite surface. The second concavity 74 further has a recessedform opened in the tangentially opposite directions. The secondconcavity 74 has a first surface 74 a directed in the rotationaldirection as well as second and third surfaces 74 b and 74 c directed inthe axial direction. In other words, a pair of upper and lower radialprojections 75 and 76 form the second concavity 74. As shown in FIG. 18,the window aperture 32 a in the input disk-shaped plate 32 is furtherprovided with a hollow 97, which is formed at each end surface 91 (i.e.,surface directed substantially in the rotational direction) of thewindow aperture 32 a and is hollowed substantially in the rotationaldirection. The hollow 97 has a first linear surface 97 a directed in therotational direction as well as second surfaces 97 b located on theopposite sides of the first surface 97 a. As shown in FIG. 18, thesecond spring seat 71 is removable in the rotational direction from theend surface 91, but is radially and axially unmovable when it is in theengaged state. More specifically, the first surface 97 a of the hollow97 is in contact with the first surface 74 a of the second concavity 74of the second spring seat 71 so that a torque can be transmitted fromthe second spring seat 71 to the end surface 91. Additionally, a portionnear the first surface 97 a is located axially between the projections75 and 76 so that the second spring seat 71 cannot axially be spacedfrom the input disk-shaped plate 32. Further, the outer peripheralsurface of the body 72 of the second spring seat 71 is in contact withthe second surface 97 b. Therefore, the second spring seat 71 cannot bespaced radially from the input disk-shaped plate 22.

As shown in FIGS. 10 and 15, the first concavity 77 is a circular formwhen viewed in the radial direction and has a bottom surface 77 a and aperipheral surface 77 b. As shown in FIG. 18, an end of the small coilspring 45 is fitted into the first concavity 77. An end surface, whichis substantially directed in the rotational direction, of one end of thesmall coil spring 45 is in contact with the bottom surface 77 a of thefirst concavity 77 to enable a transmission of torque. An outerperipheral surface of the end of the small coil spring 45 is in contactwith or close to the peripheral surface 77 b of the first concavity 77,and thus is engaged therewith so that disengagement thereof from thesecond spring seat 71 is prevented.

As shown in FIG. 19, the end surfaces 94, which are directed in therotational direction, of the windows 30 a and 31 a in the first andsecond plates 30 and 31 are further provided with hollows 98, which arefollowed in the rotational direction. The hollow 98 has a semicircularform. As shown in FIG. 19, the second spring seat 71 is removable fromthe end surface 94 in the rotational direction, but is radially andaxially unmovable in the engaged state. More specifically, the surfaces73 a of first and second projections 73 are engaged with the hollow 98in the rotational direction. Therefore, the second spring seat 71 cantransmit a torque to the end surface 94, and the second spring seat 71is not radially spaced from the first and second plates 30 and 31.Further, portions near the hollow 98 are located close to the surfaces72 a on the axially opposite sides of the body 72 respectively so thatthe second spring seat 71 is not axially spaced from first and secondplates 30 and 31.

As shown in FIG. 3, in the structure already described, since thelow-rigidity damper 37 is located between the coil springs 33neighboring to each other in the rotational direction, it is possible toprevent an unnecessary increase in diameter of the damper mechanism 6.In particular, the small coil spring 45 is located within an annularregion defined between the outermost and innermost peripheries of thecoil spring 33 when viewed in the axial direction. Therefore, diameterof the damper mechanism does not increase beyond necessary length.

Further, the small coil springs 45 are disposed close to the oppositeends, of the coil spring 33 in the rotational direction and morespecifically are arranged within the window aperture 32 a and others sothat the sizes and required space of the whole damper mechanism 6 can bereduced.

(1-4-3) Frictional Resistance Generating Mechanism

As seen in FIGS. 1 and 2, the frictional resistance generating mechanism7 functions between the crankshaft 2 and the flywheel 21 with thefriction surface in parallel with the coil springs 33 in the rotationaldirection and generates a predetermined frictional resistance(hysteresis torque) when the crankshaft 2 rotates relatively to theflywheel 21 with the friction surface. As shown in FIG. 5, thefrictional resistance generating mechanism 7 is formed of a plurality ofwashers, which are disposed between the second friction surface 21 b ofthe flywheel 21 having the friction surface and the contact portion 27of the disk-shaped plate 22 and are in contact with each other. As shownin FIGS. 5 and 6, the frictional resistance generating mechanism 7 has acone spring 43 located near the contact portion 27, an output frictionplate 44, an input friction plate 63, and a friction washer unit 61located at positions successively shifted toward the flywheel 21respectively. As described above, the disk-shaped plate 22 has thefunction of holding the frictional resistance generating mechanism 7 onthe side of the flywheel 21 with the friction surface. Therefore, it ispossible to reduce the number of parts and thus the structure can besimplified.

The cone spring 43 is provided to apply a load to each friction surfacein the axial direction and is compressed between the contact portion 27and the output friction plate 44 so that it applies an axial constantbiasing force to these members. The output friction plate 44 is providedwith claws 44 a at its outer periphery, which are engaged with therecesses 26 a in the disk-shaped plate 22, so that the output frictionplate 44 is unrotatable relatively but is axially movable with respectto the disk-shaped plate 22 and the flywheel 21 having the frictionsurface. The output friction plate 44 has an inner peripheral surface,which is in contact with the outer peripheral surface 28 a of the baseportion of the cylindrical portion 28 formed at the inner periphery ofthe disk-shaped plate 22, and thereby is radially positioned.

The friction washers 61 are formed of a plurality of arc-shaped membersaligned in the rotational direction as shown in FIG. 7. As seen in FIG.6, each friction washer 61 is held between the output friction plate 44and the second friction surface 21 b of the flywheel 21 having thefriction surface. Thus, a radial surface 61 a on the engine side of thefriction washer 61 is in slidable contact with the output friction plate44 and a radial surface 61 b on the transmission side of the frictionwasher 61 is in slidable contact with the second friction surface 21 bof the flywheel 21 having the friction surface. As shown in FIG. 24, thefriction washer 61 is provided with a concavity 62 at its outerperipheral surface 61 c. The concavity 62 is formed at acircumferentially middle portion of the friction washer 61 and has abottom surface 62 a extending in the rotational direction (i.e.,circumferential direction) as well as inclined surfaces 62 b, whichextend obliquely and radially outward from the opposite ends of thebottom surface 62 a. The inclined portions 62 b on the opposite ends ofeach concavity 62 diverge radially outward to increase thecircumferential distance between them. An inner peripheral surface 61 dof the friction washer 61 has a circumferentially middle portion, whichis close to the outer peripheral surface 28 b of the free end portion ofthe radially inner cylindrical portion 28 and a space between the innerperipheral surface 61 d and the outer peripheral surface 28 b graduallyincreases as the position moves to the circumferential end of the innerperipheral surface 61 d. Thus, the friction washer 61 is swingablearound its circumferentially middle portion with respect to thecylindrical portion 28.

As shown in FIG. 7, the input friction plate 63 has a disk-shapedportion 63 a disposed radially outside the friction washer 61. As seenin FIG. 5, the input friction plate 63 is provided with a plurality ofprojections 63 b at its outer periphery.

Referring to FIGS. 5 and 6, the projections 63 b are formedcorresponding to the recesses 26 a respectively and each have aprojected portion 63 c extending radially outward and a claw 63 dextending axially toward the engine from the end of the projectedportion 63 c. The projected portion 63 c extends radially through therecess 26 a. The claw 63 d is located radially outside the cylindricalportion 26, and extends through the recess 20 a in the cylindricalportion 20 of the disk-shaped member 13 from the axially transmissionside. The claw 63 d has a circumferential width (i.e., width in therotational direction) equal to that of the recess 20 a, therefore iscircumferentially unmovable in the recess 20 a.

As seen in FIG. 7, the disk-shaped portion 63 a of the input frictionplate 63 has an inner peripheral surface 64 which is opposed to theouter peripheral surface 61 c of the friction washer 61 with a slightspace therebetween, and a plurality of convexities 65 extending radiallyinward from the inner peripheral surface 64 into the concavities 62,respectively. The convexities 65 and the concavities 62 form anengagement portion 78 in the frictional resistance generating mechanism7. The engagement portion 78 will now be described in greater detail. Asshown in FIG. 24, the convexity 65 has a substantially square form andhas round corners 65 a. The convexity 65 is close to the bottom surface62 a of the concavity 62, and the space 79 of a predetermined angle,e.g., of 4 degrees is preferably maintained in the rotational directionbetween each corner 65 a and the neighboring inclined surface 62 b. Atotal of these torsion angles on the opposite sides is equal to anallowed maximum angle of relative rotation between the friction washer61 and the input friction plate 63. In this embodiment, the above totaltorsion angle is equal to 8 degrees (see FIG. 21) and is preferablyequal to or slightly larger than a damper operation angle which occursfrom depends on minute torsional vibrations caused by variations incombustion of the engine.

As described above, friction washer 61 is frictionally engaged with themembers on the output side, i.e., the flywheel 21 with the frictionsurface and the output friction plate 44, and is also engaged with themember on the input side, i.e., the input friction plate 63 via therotating-direction space 79 of the engagement portion 78 for allowingtorque transmission.

In the above structure, since the second friction surface 21 b of theflywheel 21 with the friction surface forms the friction surface of thefrictional resistance generating mechanism 7, the number of parts isreduced and the structure becomes simpler.

Clutch Cover Assembly

Referring again to FIGS. 1 and 2, the clutch cover assembly 8 is amechanism that biases a friction facing 54 of the clutch disk assembly 9to the first frictional surface 21 a of the flywheel 21 having thefriction surface by an elastic force. The clutch cover assembly 8 isprimarily formed of a clutch cover 48, a pressure plate 49, and adiaphragm spring 50.

The clutch cover 48 is a disk-shaped member prepared by press workingand has a radially outer portion fixed to the radially outer portion ofthe flywheel 21 with the friction surface by bolts 51.

The pressure plate 49, which is made of, e.g., cast iron, is disposedradially inside the clutch cover 48, and is axially located on thetransmission side with respect to the flywheel 21 having the frictionsurface. The pressure plate 49 has a pressing surface 49 a opposed tothe first friction surface 21 a of the flywheel 21 having the frictionsurface. The pressure plate 49 is provided with a plurality ofarc-shaped projected portions 49 b projecting toward the transmission atthe surface opposite to the pressing surface 49 a. The pressure plate 49is coupled unrotatably and axially movably to the clutch cover 48 by aplurality of arc-shaped strap plates 53. In the clutch engaged state,the strap plates 53 apply a load to the pressure plate 49 for biasingthe pressure plate 49 away from the flywheel 21 having the frictionsurface.

The diaphragm spring 50 is a disk-shaped member disposed between thepressure plate 49 and the clutch cover 48, and is formed of an annularelastic portion 50 a and a plurality of lever portions 50 b extendingradially inward from the elastic portion 50 a. The radially outerportion of the elastic portion 50 a is in axial contact with the end ofeach projected portion 49 b of the pressure plate 49 on the transmissionside.

The clutch cover 48 is provided with a plurality of tabs 48 a at itsinner periphery, which extend axially toward the engine and are bentradially outward. Each tab 48 a extends through an aperture in thediaphragm spring 50 toward the pressure plate 49. The tabs 48 a supporttwo wire rings 52, which support axially opposite sides of the radiallyinner portion of the elastic portion 50 a of the diaphragm spring 50. Inthis state, the elastic portion 50 a is axially compressed to apply anaxial force to the pressure plate 49 and the clutch cover 48.

Clutch Disk Assembly

The clutch disk assembly 9 has the friction facing 54 disposed betweenthe first friction surface 21 a of the flywheel 21 having the frictionsurface and the pressing surface 49 a of the pressure plate 49. Thefriction facing 54 is fixed to a hub 56 via a circular and annular plate55. The hub 56 has a central aperture spline-engaged with thetransmission input shaft 3.

Release Device

The release device 10 is a mechanism provided to drive the diaphragmspring 50 of the clutch cover assembly 8 to perform the clutch releasingoperation on the clutch disk assembly 9. The release device 10 isprimarily formed of a release bearing 58 and a hydraulic cylinder device(not shown). The release bearing 58 is primarily formed of inner andouter races as well as a plurality of rolling elements arrangedtherebetween and can bear radial and thrust loads. A cylindricalretainer 59 is attached to the outer race of the release bearing 58. Theretainer 59 has a cylindrical portion a first flange, and a secondflange. The cylindrical portion contacts the outer peripheral surface ofthe outer race. The first flange extends radially inward from an axialend on the engine side of the cylindrical portion and is in contact withthe surface on the transmission side of the outer race in the axialdirection. The second flange extends radially outward from an end on theengine side of the cylindrical portion in the axial direction. Thesecond flange is provided with an annular support portion, which is inaxial contact with a portion on the engine side of the radially innerend of each lever portion 50 b of the diaphragm spring 50.

A hydraulic cylinder device is primarily formed of a hydraulic chamberforming member and a piston 60. The hydraulic chamber forming member andthe cylindrical piston 60 arranged radially inside the member define ahydraulic chamber between them. The hydraulic chamber can be suppliedwith a hydraulic pressure from a hydraulic circuit. The piston 60 has asubstantially cylindrical form and has a flange which is in axialcontact with a portion on the transmission side of the inner race of therelease bearing 58. When the hydraulic circuit supplies a hydraulicfluid into the hydraulic chamber, the piston 60 axially moves therelease bearing 58 toward the engine.

Coupling between First and Second Flywheel Assemblies

As already described, each of the first and second flywheel assemblies 4and 5 is independent of each other and is axially and removablyattached. More specifically, the first and second flywheel assemblies 4and 5 are engaged together owing to engagement between the cylindricalportion 20 and the input friction plate 63, between the disk-shapedmember 13 and the contact portion 27 (relative rotation suppressingmechanism 24), between the second plate 31 and the flywheel 21 with thefriction surface (coupling structure 34), and between the support plate39 and the flywheel 21 with the friction surface (bushing 47), which arelocated at positions shifted successively and radially inward in thisorder. These assemblies 4 and 5 are axially movable through apredetermined range with respect to each other. More specifically, thesecond flywheel assembly 5 is axially movable with respect to the firstflywheel assembly 4 between a position, where the contact portion 27 isslightly spaced from the friction member 19, and a position, where thecontact portion 27 is in contact with the friction member 19.

(2) Operation

(2-1) Torque Transmission

In this clutch device 1, a torque is supplied from the engine to thecrankshaft 2 to the flywheel damper 11, and is transmitted from thefirst flywheel assembly 4 to the second flywheel assembly 5 via thedamper mechanism 6. In the damper mechanism 6, the torque is transmittedthrough the input disk-shaped plate 32, small coil springs 45, coilsprings 33, and output disk-shaped plates 30 and 31 in this order.Further, the torque is transmitted from the flywheel damper 11 to theclutch disk assembly 9 in the clutch engaged state and is finallyprovided to the input shaft 3.

(2-2) Absorbing and Damping of Torsional Vibrations

When the clutch device 1 receives the combustion variations from theengine, the damper mechanism 6 operates to rotate the input disk-shapedplate 32 relatively to the output disk-shaped plates 30 and 31 in thedamper mechanism 6 so that the small coil springs 45 and the coilsprings 33 are compressed. Further, the frictional resistance generatingmechanism 7 generates a predetermined hysteresis torque. Through theforegoing operations, the torsional vibrations are absorbed and damped.

As seen in FIGS. 8 and 9, more specifically, the small coil springs 45and the coil spring 33 are compressed between the end surfaces 91 of thewindow aperture 32 a in the input disk-shaped plate 32 and the endsurfaces 94 of the windows 30 a and 31 a in the output disk-shapedplates 30 and 31 in the rotational direction. Further, in a region of asmall torsion angle, the two small coil springs 45 are compressed toexhibit characteristics of a low rigidity. In this state, the coilspring 33 is hardly compressed. Moreover, when the input disk-shapedplate 32 rotates in the rotational direction R1 relatively against thefirst and second plates 30 and 31 from the neutral position illustratedin FIG. 22, the small coil spring 45 located on the forward side in therotational direction R2 with respect to the coil spring 33 is compressedin the rotational direction between the first and second spring seats 70and 71. In this operation, the torque is transmitted from the endsurface 91, located on the forward side in the rotational direction R2,of the window aperture 32 a in the input disk-shaped plate 32 to thecoil spring 33 via the second spring seat 71 on the forward side in therotational direction R2, the small coil spring 45 and the first springseat 70, and further is transmitted through the first spring seat 70 onthe forward side in the rotational direction R1 to the end surfaces 94on the forward side in the rotational direction R2 of the windows 30 aand 31 a in the plates 30 and 31. Thereafter, as shown in FIG. 23, theend surface 91 on the forward side in the rotational direction of thewindow aperture 32 a comes into contact with the second support surface81 b of the support portion 81 of the first spring seat 70. At the sametime, a portion of the body 72 of the second spring seat 71 comes intocontact with the radial surface 89 on the radially outer side of theconcavity 85 of the first spring seat 70. When this contact occurs, thesmall coil springs 45 are no longer compressed. As described above,since the small coil springs 45 are disposed within the window aperture32 a in the input disk-shaped plate 32 and are aligned in the rotationaldirection with respect to the coil spring 33, the required spaced can besmall and the structure can be relatively simple. Further, the radialsurface 89 on the radially outer side of the first spring seat 70 (i.e.,the surface located radially outside the small coil spring) is inclinedto increase the space from the small coil spring 45 as the positionmoves toward the end surface 91. Therefore, the first spring seat 70does not restrict the radial position of the small coil spring 45 whenthe small coil spring 45 is compressed. Consequently, the small coilspring 45 does not slide on the first spring seat 70 so that frictionhardly occurs therebetween. Further, the small coil spring 45 maintainsan intended position when compressed, and thus can provide an intendedload.

Subsequently, the coil spring 33 is compressed to producecharacteristics of a high rigidity in a region of a large torsion angle.More specifically, the four coil springs 33 are compressed in parallel.

Referring now to FIG. 5, in the frictional resistance generatingmechanism 7, the friction washer 61 rotates together with the inputfriction plate 63, and thus rotates relatively to the output frictionplate 44 and the flywheel 21 having the friction surface. Consequently,the friction washer 61 slides on the output friction washer 44 and theflywheel 21 having the friction surface to generate a relatively largefrictional resistance.

(2-2-1) Minute Torsional Vibrations

The operation of the damper mechanism 6, which is performed when minutetorsional vibrations due to the combustion variations of the engine areapplied to the clutch device 1, will now be described with reference toa mechanical circuit diagram of FIG. 20 as well as torsioncharacteristic diagrams of FIGS. 21, 27, 28 and 29. In FIG. 20, thefirst and second spring seats 70 and 71 are not shown.

When minute torsional vibrations are applied, the input friction plate63 in the frictional resistance generating mechanism 7 rotatesrelatively to the friction washer 61 through an angle, which correspondsto the minute space in the rotational direction between the concavity 65and convexity 62. Thus, the friction washer 61 is not driven by theinput friction plate 63, and therefore, does not rotate relatively theflywheel 21 having the friction surface and others. Consequently, a highhysteresis torque does not occur in response to the minute torsionalvibrations. According to the torsion characteristic diagram of FIG. 21,the coil spring 33 operates, e.g., in “AC2 HYS”, but no sliding occursin the frictional resistance generating mechanism 7. Thus, only ahysteresis torque, which is much smaller than an ordinary hysteresistorque, can be obtained in a predetermined torsion angle range. Asdescribed above, the minute rotating-direction space is provided toprevent the operation of the frictional resistance generating mechanism7 in the predetermined angle range in the torsion characteristics.Therefore, the levels of vibrations and noises can be significantlylowered.

The operation of driving the friction washer 61 by the input frictionplate 63 will now be described in connection with an initial transitionstate and a usual state. The input friction plate 63 rotates relativelyto the friction washer 61 in the rotational direction R1 from theneutral position in FIG. 24, as described below. In FIG. 24, the innerperipheral surface 61 d of the friction washer 61 is slightly spacedfrom the outer peripheral surface 28 b of the cylindrical portion 28except for its circumferentially middle portion (i.e., the middleportion in the rotational direction).

When the torsion angle increases, the convexity 65 comes into contactwith the wall surface of the convexity 62 as shown FIG. 25. Morespecifically, the corner 65 a of the convexity 65 comes into contactwith the inclined surface 62 b of the convexity 62. In this state, acomponent of a force applied from the convexity 65 to the concavity 62occurs to move the friction washer 61 radially inward. When the torsionangle increases from the state shown in FIG. 25, the portion, which islocated on the forward side in the rotational direction R1, of thefriction washer 61 moves radially inward and the portion on the forwardside in the rotational direction R2 moves radially outward. Thus, asshown in FIG. 26, the inner peripheral surface 61 d of the forwardportion of the friction washer 61 in the rotational direction R1 movestoward the outer peripheral surface 28 b of the cylindrical portion 28and the inner peripheral surface 61 d of the forward portion, in therotational direction R2, moves away from the outer peripheral surface 28b of the cylindrical portion 28. During the above operation, the forcefor moving the friction washer 61 radially inwardly increases. Thus, aneffective radius of the friction surface of the friction washer 61gradually increases; thereby the frictional resistance graduallyincreases. After the inner peripheral surface 61 d of the forwardportion of the friction washer 61 the rotational direction R1 comes intocontact with the outer peripheral surface 28 b of the cylindricalportion 28 as shown in FIG. 26, the friction washer 61 moves only in therotational direction thereafter.

The above can be summarized as follows. The friction washer 61 is drivenby the input friction plate 63 in the two regions, i.e., the firstregion, in which the effective radius of the friction surface and thefrictional resistance gradually increase and the second region, in whichthe effective radius of the friction surface and the frictionalresistance are constant. In this embodiment, the first region has asize, e.g., of about 2°.

In summary, the input friction plate 63 and the engagement portion 78 ofthe friction washer 61 (specifically, the convexity 65 and the concavity62) are configured to ensure the first region for gradually increasingthe effective radius of the friction surface of the friction washer 61and the second region for keeping the effective radius of the frictionsurface of the friction washer 61 at a constant value.

Consequently, when the operation angle of the torsional vibrations doesnot exceed a predetermined angle (e.g., of 8°) of the engagement portion78, a large frictional resistance (high hysteresis torque) does notoccur, and only a region A of a low frictional resistance is obtained asillustrated in FIG. 27. When the operation angle of the torsionalvibrations is in a range between the predetermined angle (e.g., of 8°)of the rotating-direction space 79 of the engagement portion 78 and anangle (e.g., 10°) larger than this predetermined angle (e.g., 8°) by africtional resistance change angle (e.g., 2°), a region B in which thefrictional resistance gradually increases, occurs at each end of theregion A of the low frictional resistance as illustrated in FIG. 28.When the operation angle of the torsional vibrations is larger than theangle equal to a sum of the predetermined angle of the engagementportion 78 and the frictional resistance change angle, the region B, inwhich the frictional resistance gradually increases, and a region C, inwhich a large constant frictional resistance occurs, are formed on eachside of the region A of the low frictional resistance as illustrated inFIG. 29.

(2-2-2) Large-Angle Torsional Vibrations

Referring now to FIGS. 5, 7 and 21, described before, when the torsionangle of torsional vibrations is large, the friction washer 61 slides onthe flywheel 21 having the friction surface and the disk-shaped plate22. Thereby, a frictional resistance of a constant magnitude occursthroughout the first and second stage.

At an end of the torsion angle range (i.e., the position where thedirection of the vibration changes), operations are performed asfollows. On the right end in the torsion characteristic diagram of FIG.21, the friction washer 61 is in the position shifted to the maximumextent in the rotational direction R2 with respect to the input frictionplate 63. When the disk-shaped member 13 rotates relatively to theflywheel 21 having the friction surface in the rotational direction R2,the friction washer 61 rotates relatively to the input friction plate 63throughout the angle range of the rotating-direction space 79 betweenthe convexity 65 and the concavity 62. During this operation, thefriction washer 61 does not slide on the member on the output side, i.e.the flywheel 21 having the friction surface, so that the region A (e.g.,of 8°) of a low frictional resistance is obtained, i.e. friction is notgenerated between the friction washer 61 and the flywheel 21. When therotating-direction space 79 of the engagement portion 78 disappears, theinput friction plate 63 starts to drive the friction washer 61. Thereby,the friction washer 61 rotates relatively to the output friction plate44 and the flywheel 21 having the friction surface as well as thedisk-shaped plate 22. This produces the region B, e.g., of 2°, in whichthe frictional resistance gradually (and thus smoothly) increases, asalready described, then produces the region C of a large constantfrictional resistance.

As described above, the region B, in which the frictional resistancegradually increases, is provided in an initial stage of the operation ofgenerating a large frictional resistance. Since the large frictionalresistance rises smoothly, a wall of a high hysteresis torque does notexist when generating the large hysteresis torque. Thereby, hitting ortapping noises of claws, which may occur when a high hysteresis torqueoccurs, can be reduced in the frictional resistance generatingmechanism, which is provided with the minute space in the rotationaldirection for absorbing the minute torsional vibrations.

In particular, since the structure according to the invention employs asingle kind of friction washers (i.e., washers 61) for generating anintermediate frictional resistance, the kinds of the friction memberscan be reduced in number. Since the friction washer 61 has a simplearc-shaped form, the manufacturing cost thereof can be low.

(3) Clutch Engaging and Releasing Operations

As seen in FIGS. 1 and 2, when the hydraulic circuit (not shown)supplies the hydraulic fluid into the hydraulic chamber of the hydrauliccylinder, the piston 60 axially moves toward the engine. Thereby, therelease bearing 58 axially moves the radially inner end of the diaphragmspring 50 toward the engine. Consequently, the elastic portion 50 a ofthe diaphragm spring 50 is spaced from the pressure plate 49. Thereby,the pressure plate 49 biased by the strap plates 53 moves away from thefriction facing 54 of the clutch disk assembly 9 so that the clutch isreleased.

In the clutch release operation, the release bearing 58 applies an axialload which is directed toward the engine to the clutch cover assembly 8and this load axially biases and moves the second flywheel assembly 5toward the engine. Thereby, the contact portion 27 of the disk-shapedplate 22 in the relative rotation suppressing mechanism 24 is pressedagainst the friction mechanism 19 and is frictionally engaged with thedisk-shaped member 13. Thus, the second flywheel assembly 5 becomesunrotatable with respect to the first flywheel assembly 4. In otherwords, the second flywheel assembly 5 is locked with respect to thecrankshaft 2 so that the damper mechanism 6 does not operate.Accordingly, when the rotation speed passes through the resonance pointin a low speed range (e.g., from 0 to 500 rpm) during a start or stopoperation of the engine, it is possible to suppress the breakage of thedamper mechanism 6 as well as noises and vibrations, which may be causedby the resonance when releasing the clutch.

In this operation, since the damper mechanism 6 is locked by using theload applied from the release device 10 in the clutch releasingoperation, the structure becomes simpler. In particular, since therelative rotation suppressing mechanism 24 is formed of the membershaving simple forms such as the disk-shaped member 13 and thedisk-shaped plate 22, a special structure is not required.

(3) Stop Mechanism of Damper Mechanism

As already described, the elastic coupling mechanism 29 of the dampermechanism 6, which elastically couples the second flywheel assembly 5 tothe crankshaft 2 in the rotating direction, is formed of the pair ofoutput-side disk-shaped plates 30 and 31, the input-side disk-shapedplate 32, and a plurality of coil springs 33. As seen in FIG. 3,further, a stop mechanism 90 of the damper mechanism 6 is formed of aplurality of plate coupling portions 40 formed at the outer periphery ofthe disk-shaped main body of the second plate 31 and the contactportions 32 c formed at the outer periphery of the input-side disk-likeplate 32.

The stop mechanism 90 described above has the following advantages.

(3-1) Since the axially extending portion 41 of the plate couplingportion 40 has a plate-like form, a circumferential angle thereof can beshorter than that in a conventional stop pin.

(3-2) The axially extending portion 41 of the plate coupling portion 40has a radial length much smaller than that of the conventional stop pin.More specifically, the radial length of the stop mechanism 90 is equalto the thickness of the pair of output-side disk-shaped plates 30 and31. This means that the radial length of the stop mechanism 90 issubstantially restricted to a small value corresponding to the platethickness.

Owing to the above, as shown in FIG. 3, the plate coupling portion 40 isarranged at the outer peripheral portion, i.e., the radially outermostposition of the input disk-shaped plate 32, and is located radiallyoutside the outer periphery of the window aperture 32 a. As describedabove, the plate coupling portion 40, i.e., the stop mechanism 90 takesa position radially different from the window aperture 32 a so that thestop mechanism 90 does not circumferentially interfere with the windowaperture 32 a. Consequently, it is possible to increase both the maximumtorsion angle of the damper mechanism 6 and the torsion angle of thecoil spring 33. More specifically, the plate coupling portion 40 movesto a position radially outside the window aperture 32 a, and further cansubstantially move to a position radially outside a circumferentialcenter of the window aperture 32 a.

In a conventional structure, the stop mechanism and the window apertureare located at the radially same position. In this structure, thetorsion angle of the damper mechanism restricts the circumferentialangle of the window aperture, and vice versa so that it is impossible toincrease the maximum angle of the damper mechanism and to lower therigidity of the springs.

In particular, the radial length of the stop mechanism 90 is muchshorter than that of the conventional stop pin. Therefore, provision ofthe stop mechanism radially outside the window aperture 32 a does notremarkably increase the outer diameter of the output-side disk-shapedplates 30 and 31. Also, it does not reduce the radial length of thewindow aperture 32 a.

Alternate Embodiments

Alternate embodiments will now be explained. In view of the similaritybetween the first and alternate embodiments, the parts of the alternateembodiments that are identical to the parts of the first embodiment willbe given the same reference numerals as the parts of the firstembodiment. Moreover, the descriptions of the parts of the alternateembodiments that are identical to the parts of the first embodiment maybe omitted for the sake of brevity.

Second Embodiment

Referring to FIGS. 30 to 45, a second embodiment of the invention willbe described. Basic structures of the clutch device and the dampermechanism in the second embodiment are substantially the same as thosein the first embodiment as a whole, therefore, a frictional resistancegenerating mechanism 107 will be described hereinafter.

As seen in FIG. 30, the frictional resistance generating mechanism 107functions between a crankshaft and a flywheel 121 having the frictionsurface in parallel with coil springs 133 and generates a predeterminedfrictional resistance (hysteresis torque) when the crankshaft rotatesrelatively to the flywheel 121 having the friction surface. The flywheelassembly 104 and annular member 114 are configured the same as orsubstantially the same as the flywheel assembly 4 and annular member 14of the first embodiment. As seen in FIG. 30, the frictional resistancegenerating mechanism 107 is formed of a plurality of washers, which aredisposed between a second friction surface 121 b of the flywheel 121having the friction surface and a contact portion 127 of a disk-shapedplate 122, and are in contact with each other. As shown in FIGS. 30 and31, the frictional resistance generating mechanism 107 has a cone spring143, an output friction plate 144, a first friction washer 161, a firstfriction washer 162, an input friction plate 163, a second frictionwasher 164, and a second friction washer 165. The cone spring 143 islocated near the contact portion 127. The first friction washer 161 hasa high friction coefficient. The first friction washer 162 has a lowfriction coefficient. The second friction washer 164 has a low frictioncoefficient. The second friction washer 165 has a high frictioncoefficient. In the aforementioned order, the members of the frictionalresistance generating mechanism 107 are located at positionssuccessively shifted toward the flywheel 121, respectively. As describedabove, the disk-shaped plate 122 has the function of holding thefrictional resistance generating mechanism 107 on the side of theflywheel 121 having the friction surface. Therefore, it is possible toreduce the number of parts to simplify the structure.

The cone spring 143 is provided apply an axial load to each frictionsurface and is compressed between the contact portion 127 and the outputfriction plate 144 so that it applies an axial biasing force to thesemembers. The output friction plate 144 is provided with claws 144 a atits outer periphery, which are engaged with recesses 126 a in thedisk-shaped plate 122 so that the output friction plate 144 isunrotatable but is axially movable with respect to the disk-shaped plate122 and the flywheel 121 having the friction surface. The outputfriction plate 144 has an inner peripheral surface, which is in contactwith an outer peripheral surface 128 a of the base portion of thecylindrical portion 128 formed at the outer periphery of the disk-shapedplate 122, and thereby is radially positioned.

The first friction washer 161 having a high friction coefficient is anannular member as shown in FIGS. 32 and 33. As shown in FIG. 31, thefirst friction washer 161 is located between the output friction plate144 and the first friction washer 162 having a low friction coefficient.The first high-friction-coefficient friction washer 161 is formed of acore plate 171 and a friction facing 172 affixed thereto. The core plate171 is an annular member. The friction facing 172 is formed of aplurality of arc-shaped members affixed to the axial surface on theengine side of the core plate 171, and is in contact with the outputfriction plate 144. The core plate 171 and the friction facing 172 havesubstantially the same inner diameters, and also have substantially thesame outer diameters. As seen in FIGS. 32 and 33, the core plate 171 isprovided with projected portions 171 a at its outer periphery projectingaxially toward the transmission. The core plate 171 is provided with aplurality of apertures 171 b at its body. The core plate 171 is providedwith a plurality of projections 171 c at its inner periphery extendingradially inward. The friction facing 172 is provided with apertures 172a corresponding to the apertures 171 b respectively.

As shown in FIG. 34, the first low-friction-coefficient friction washer162 is formed of a plurality of arc-shaped members, and as seen in FIG.31, is located between the first high-friction-coefficient frictionwasher 161 and the input friction plate 163. The firstlow-friction-coefficient friction washer 162 is preferably made ofplastics. Referring again to FIG. 34, the first low-friction-coefficientfriction washer 162 is provided with a plurality of projected portions162 a at its radial surface on the engine side. The projected portions162 a are inserted into and engaged with the apertures 171 b and 172 ain the first high-friction-coefficient friction washer 161. Owing tothis engagement, the first high-friction-coefficient friction washer 161and first low-friction-coefficient friction washer 162 rotate together.The first low-friction-coefficient friction washer 162 is provided witha plurality of projections 162 b at its inner periphery projectedradially inward.

The input friction plate 163 has a disk-shaped portion 163 a locatedaxially between the first low-friction-coefficient friction washer 162and the second low-friction-coefficient friction washer 164. As shown inFIG. 35, the input friction plate 163 is provided with a plurality ofprojections 163 b at its outer periphery, as shown in FIG. 35. Theprojections 163 b are formed corresponding to the recesses 126 a,respectively, and each are formed of a projected portion 163 c projectedradially outward and a claw 163 d extending axially toward the enginefrom the end of the projected portion 163 c. The projected portion 163 cextends radially through the recess 126 a. The claw 163 d is locatedradially outside the cylindrical portion 126, and extends axiallythrough the recess 126 a in the cylindrical portion 120 of thedisk-shaped member 113 toward the engine. As shown in FIGS. 39 and 40,the claw 163 d and the recess 120 a form a first rotating-directionengagement portion 181 between the disk-shaped member 113 and the outputfriction plate 144. The disk-shaped portion 163 a of the input frictionplate 163 is provided with a plurality of recesses 163 e at its outerperiphery, and is provided with a plurality of projections 163 f at itsinner periphery extending radially inward.

In the first rotating-direction engagement portion 181, the width in therotational direction of the claw 163 d is shorter than that of therecess 120 a so that the claw 163 d can move a predetermined anglewithin the recess 120 a. This means that the input friction plate 163 ismovable through a predetermined angle range with respect to thedisk-shaped member 113. More specifically, as shown in FIG. 40, arotating-direction space 146 of a torsion angle of θ1 is ensured on theforward side, in the rotational direction R2, of the claw 163 d, and arotating-direction space 147 of a torsion angle of θ2 is formed on theforward side, in the rotational direction R1, of the claw 163 d.Consequently, the total torsion angle, i.e., the sum of the torsionangles of θ1 and θ2 provides the predetermined angle, by which the inputfriction plate 163 can rotate relatively to the disk-shaped member 113.In this embodiment, the total torsion angle is equal to 8° (see FIG.42). This total torsion angle is preferably in a range slightlyexceeding a damper operation angle, which is caused by minute torsionalvibrations due to combustion variations of the engine.

As seen in FIG. 31, the second low-friction-coefficient friction washer164 is formed of a plurality of arc-shaped members similar or identicalto the first low-friction-coefficient friction washer 162 and is locatedbetween the input friction plate 163 and the secondhigh-friction-coefficient friction washer 165. The secondlow-friction-coefficient friction washer 164 is preferably made ofplastics. The second low-friction-coefficient friction washer 164 isprovided with a plurality of projected portions 164 a at its surface onthe transmission side.

The second high-friction-coefficient friction washer 165 is an annularmember as shown in FIGS. 36 and 37, and is located between the secondlow-friction-coefficient friction washer 164 and the second frictionsurface 121 b of the flywheel 121 having the friction surface. Thesecond high-friction-coefficient friction washer 165 is formed of a coreplate 173 and a friction facing 174 affixed thereto. The core plate 173is an annular member. The friction facing 174 is formed of a pluralityof arc-shaped members affixed to the surface on the engine side of thecore plate 173 and is in contact with the second friction surface 121 bof the flywheel 121 having the friction surface. The inner diameter ofthe core plate 173 is substantially equal to the inner diameter of thefriction facing 174, and the inner diameter of the core plate 173 isslightly larger than the inner diameter of the friction facing 174. Thecore plate 173 is provided with a plurality of apertures 173 a at itsbody. The core plate 173 is provided with a plurality of projections 173c at the inner periphery of the body extending radially inward. Thefriction facing 174 is provided with apertures 174 a corresponding tothe respective apertures 173 a. The projected portions 164 a of thesecond low-friction-coefficient friction washer 164 are inserted intoand engaged with these apertures 171 b and 172 a. Owing to thisengagement, the second high-friction-coefficient friction washer 165 andsecond low-friction-coefficient friction washer 164 rotate together.

The core plate 173 is provided with a plurality of circumferentiallyspaced recesses 173 b at its outer periphery. The axially projectedportions 171 a already described are inserted into and engaged with therecesses 173 b, respectively, so that the firsthigh-friction-coefficient friction washer 161 and the secondhigh-friction-coefficient friction washer 165 rotate together. Theaxially projected portions 171 a are inserted into the recesses 163 eformed at the outer periphery of the disk-shaped portion 163 a of theinput friction plate 163, respectively. As described above, the axiallyprojected portions 171 a and the recesses 163 e form a secondrotating-direction engagement portion 182 between the input frictionplate 163 and the friction washers 161, 162, 164 and 165, as shown inFIG. 41.

In the second rotating-direction engagement portion 182, the width inthe rotational direction of the axially projected portion 171 a isshorter than that of the recess 163 e so that the axially projectedportion 171 a can move a predetermined angle within the recess 163 e.This means that the input friction plate 163 is movable through apredetermined angle range with respect to the friction washers 161, 162,164, and 165. More specifically, as shown in FIG. 40, arotating-direction space 185 of a torsion angle of θ3 is ensured on theforward side, in the rotational direction R1, of the axially projectedportion 171 a, and a rotating-direction space 186 of a torsion angle ofθ4 is formed on the forward side, in the rotational direction R2, of theprojected portion 171 a. Consequently, the total torsion angle, i.e.,the sum of the torsion angles of θ3 and θ4 provides the predeterminedangle, by which the input friction plate 163 can rotate relatively tothe friction washers 161, 162, 164, and 165. In this embodiment, thetotal torsion angle is equal to 2° (see FIG. 42).

Referring again to FIG. 31, the frictional resistance generatingmechanism 107 further includes a bushing 166. The bushing 166 is formedof a plurality of members for radially supporting the respective washerswith respect to the inner cylindrical portion 128 and is disposedradially between the inner peripheries of the washers and the innercylindrical portion 128. As seen in FIG. 38, the bushing 166 has apredetermined axial length, and each portion thereof has an arc-shapedform when viewed in the axial direction. The bushing 166 has a smoothinner peripheral surface, which is rotatably supported by an outerperipheral surface 128 b of the free end portion of the innercylindrical portion 128. The inner cylindrical portion 128 is providedwith a plurality of concavities 166 a at its outer peripheral surface.Each concavity 166 a is concaved radially inward, and extends throughoutthe axial length of the portion 128. Into the concavities 166 a,projections of various members are fitted, and specifically, theprojections 171 c of the first high-friction-coefficient friction washer161, the projections 162 b of the first low-friction-coefficientfriction washer 162, projections 164 b of the secondlow-friction-coefficient friction washer 164, the projections 173 c ofthe second high-friction-coefficient friction washer 165, and others arefitted and engaged. A relatively large space in the rotational directionis ensured in the engagement portion, where each washer is engaged withthe bushing 166 so that the foregoing function of the secondrotating-direction engagement portion 182 may not be impeded.

As seen in FIG. 31, in the frictional resistance generating mechanism107 described above, the engagement of the disk-shaped portion 163 a ofthe input friction plate 163 with the first and secondlow-friction-coefficient friction washers 162 and 164 provides a firstfrictional resistance generating portion 188. Further, a secondfrictional resistance generating portion 189 is provided by theengagement between the first high-friction-coefficient friction washer161 and the output friction plate 144 as well as the engagement betweenthe second high-friction-coefficient friction washer 165 and theflywheel 121 having the friction surface.

In the above structure, since the second friction surface 121 b of theflywheel 121 with the friction surface forms the friction surface of thefrictional resistance generating mechanism 107, this reduces the numberof parts and simplifies the structure.

(2) Operation

When the clutch device receives the combustion variations from theengine, the damper mechanism operates to rotate the input disk-shapedplate 132 relatively to the output disk-shaped plates 130 and 131 in thedamper mechanism so that the plurality of coil springs 133 and othersare compressed between them. Further, the frictional resistancegenerating mechanism 107 generates a predetermined hysteresis torque.Through the foregoing operations, the torsional vibrations are absorbedand damped. More specifically, the coil springs 133 are compressedbetween the circumferential ends of the window apertures in the inputdisk-shaped plate 132 and the circumferential ends of the windows in theoutput disk-shaped plates 130 and 131.

As seen in FIGS. 30 and 31, in the frictional resistance generatingmechanism 107, the first and second high-friction-coefficient frictionwashers 161 and 165 rotate together with the disk-shaped member 113 viathe input friction plate 163 therebetween, and rotates relatively to theoutput friction plate 144 and the flywheel 121 having the frictionsurface. Consequently, sliding occurs between the output friction plate144 and the first high-friction-coefficient friction washer 161, andalso occurs between the second high-friction-coefficient friction washer165 and the flywheel 121 having the friction surface. Thus, the secondfrictional resistance generating mechanism 189 operates to generate arelatively large frictional resistance.

Description will now be given on the operation of the damper mechanism,which is performed when minute torsional vibrations due to thecombustion variations of the engine are applied to the clutch device,with reference to a mechanical circuit diagram of FIG. 41 and a torsioncharacteristic diagram of FIG. 42. When minute torsional vibrations areapplied to the damper mechanism, in which the coil springs 133 are inthe compressed state, the input friction plate 163 of the frictionalresistance generating mechanism 107 rotates in the minuterotating-direction space (146 and 147), which is defined in the recess120 a of the cylindrical portion 120 of the disk-shaped member 113 bythe claw 163 d, and therefore, relatively rotates the disk-shaped member113. Thus, the disk-shaped member 113 does not drive the input frictionplate 163 and the friction washers 161, 162, 164, and 165. Therefore,neither of the first or second frictional resistance generating portions188 and 189 generates a frictional resistance (see FIG. 43).Consequently, a high hysteresis torque does not occur in response to theminute torsional vibrations. For example, in “AC2 HYS” illustrated inthe torsion characteristic diagram of FIG. 42, the coil springs 133operate, but no sliding occurs in the frictional resistance generatingmechanism 107. In the predetermined torsion angle range, only ahysteresis torque, which is much smaller than an ordinary hysteresistorque, can be obtained. As described above, the structure employs theminute rotating-direction space (146 and 147), which does not operatethe frictional resistance generating mechanism 107 within apredetermined angle range in the torsion characteristics. Therefore, thelevels of the vibrations and noises can be significantly reduced.

When the torsion angle of the minute torsional vibrations exceeds theangle of the first rotating-direction engagement portion 181, therotating-direction space (146 and 147) disappears in the firstrotating-direction engagement portion 181, and then the disk-shapedmember 113 drives the input friction plate 163 in the rotationaldirection. Consequently, the input friction plate 163 rotates relativelyto the first and second low-friction-coefficient friction washers 162and 164. Thus, the first frictional resistance generating portion 188operates to generate a relatively small frictional resistance (see FIG.44).

When the torsion angle of the torsional vibrations further increases,the circumferential space (185 and 186) in the second rotating directionengagement portion 182 disappears and the input friction plate 163drives the friction washers 161, 162, 164, and 165 in the rotationaldirection. Thereby, the friction washers 161, 162, 164 and 165 rotaterelatively to the output friction plate 144 and the flywheel 121 havingthe friction surface. Thus, the second frictional resistance generatingportion 189 operates to generate a relatively large frictionalresistance (see FIG. 45).

(2-2-2) Large-Angle Torsional Vibrations

As already described, when the torsion angle of the torsional vibrationsis large sliding occurs between the output friction plate 144 and thefirst high-friction-coefficient friction washer 161 and sliding alsooccurs between the second high-friction-coefficient friction washer 165and the flywheel 121 having the friction surface.

At an end of the torsion angle range (i.e., the position where thedirection of the vibration changes), operations are performed asfollows. On the right end in the torsion characteristic diagram of FIG.42, the input friction plate 163 is in the position shifted in therotational direction R2 to the maximum extent with respect to thedisk-shaped member 113 and the friction washers 161, 162, 164, and 165are in the positions shifted to the maximum extent in the rotationaldirection R2 with respect to the input friction plate 163. When thedisk-shaped member 113 rotates relatively to the flywheel 121 having thefriction surface in the rotational direction R2, the disk-shaped member113 angularly moves throughout the rotating-direction space (146 and147) of the first rotating-direction engagement portion 181 and rotatesrelatively to the input friction plate 163. During this operation,neither of the first and second frictional resistance generatingportions 188 and 189 generate the frictional resistance. When therotating-direction space (146 and 147) in the first rotating-directionengagement portion 181 disappears, the disk-shaped member 113 drives theinput friction plate 163. Thereby, the input friction plate 163angularly moves throughout the rotating-direction space (185 and 186) inthe second rotating-direction engagement portion 182, and rotatesrelatively to the first and second low-friction-coefficient frictionwashers 162 and 164. During this operation, the first frictionalresistance generating portion 188 operates to generate a relativelysmall frictional resistance.

As the rotating-direction space (185 and 186) in the secondrotating-direction engagement portion 182 disappears, the input frictionplate 163 drives the friction washers 161, 162, 164, and 165. Thereby,the friction washers 161, 162, 164, and 165 rotate relatively to theoutput friction plate 144 and the flywheel 121 having the frictionsurface. Thereby, the second frictional resistance generating portion189 operates to generate a large frictional resistance.

As described above, the first frictional resistance generating portion188 generates a frictional resistance of an intermediate magnitudewithin the torsion angle range of the rotating-direction space (185 and186) in the second rotating-direction engagement portion 182 before thesecond frictional resistance generating portion 189 operates to generatea large frictional resistance. As described above, the large frictionalresistance rises in a multi-step or stepwise fashion so that a wall of ahigh hysteresis torque does not exist when generating the largefrictional resistance. Thereby, hitting or tapping noises of claws,which may occur when a high hysteresis torque occurs, can be reduced inthe frictional resistance generating mechanism which is provided withthe minute space in the rotational direction for absorbing the minutetorsional vibrations.

In the prior art, because the frictional resistance generating mechanism107 does not have the second rotating-direction engagement portion 182and the first frictional resistance generating portion 188, the secondfrictional resistance generating portion 189 starts the operation whenthe claw 163 d in the first rotating-direction engagement portion 181comes into contact with the recess 120 a in the disk-shaped member 113.Thereby, a high hysteresis torque rapidly occurs so that the claws hitthe wall to generate the hitting noises.

Third Embodiment

(3-1) Structure of Frictional Resistance Generating Mechanism

Referring initially to FIG. 46, description will now be given on africtional resistance generating mechanism 207 according to a thirdembodiment of the invention. This frictional resistance generatingmechanism 207 differs from the frictional resistance generatingmechanism 107 of the second embodiment in that the firstrotating-direction engagement portion in the second embodiment isarranged outside the washers and others which are axially stackedtogether, but the first rotating-direction engagement portion in thisembodiment is arranged within axially stacked washers and others.

The following description will be primarily given on the frictionalresistance generating mechanism 207, and other portions of the clutchdevice will be omitted. Parts and portions corresponding to those in thepreceding embodiments are indicated by reference numbers bearing “2” atthe hundred's place.

The frictional resistance generating mechanism 207 is configured tooperate in the rotational direction between a crankshaft and a flywheel221 having a friction surface, and in parallel with coil springs 233 andto generate a predetermined frictional resistance (hysteresis torque)when relative rotation occurs between the crankshaft and the flywheel221 having a friction surface. The frictional resistance generatingmechanism 207 is formed of a plurality of washers, which are in contactwith each other and are disposed between a second friction surface 221 bof the flywheel 221 having the friction surface and a contact portion227 of the disk-shaped plate 222. As shown in FIGS. 46 and 47, thefrictional resistance generating mechanism 207 has a cone spring 243located near the contact portion 227, an output friction plate 244, afirst friction washer 261 having a high friction coefficient, a firstfriction washer 262 having a low friction coefficient, an input frictionplate 263, a second friction washer 264 having a low frictioncoefficient, and a second friction washer 265 having a high frictioncoefficient. In this order, these members are located at positionssuccessively shifted toward the flywheel 221 respectively.

The cone spring 243 is provided to apply an axial load to each frictionsurface and is compressed between the contact portion 227 and the outputfriction plate 244 so that it applies an axial biasing force to thesemembers. The output friction plate 244 is provided with claws 244 a atits outer periphery, which are engaged with the recesses 226 a in thedisk-shaped plate 222, so that the output friction plate 244 isunrotatable but is axially movable with respect to the disk-shaped plate222 and the flywheel 221 having the friction surface. The outputfriction plate 244 has an outer peripheral surface, which is in contactwith an inner peripheral surface 228 a of the base portion of acylindrical portion 228 formed at the outer periphery of the disk-shapedplate 222, and thereby is radially positioned.

The first friction washer 261 having a high friction coefficient is anannular member, and is located between the output friction plate 244 andthe first friction washer 262 having a low friction coefficient. Thefirst high-friction-coefficient friction washer 261 is formed of a coreplate 271 and a friction facing 272 affixed thereto. The core plate 271is an annular member. The friction facing 272 is formed of a pluralityof arc-shaped members affixed to the radial surface on the engine sideof the core plate 271, and is in contact with the output friction plate244. The core plate 271 is provided with a plurality of apertures 271 aextending in the rotational direction.

The first low-friction-coefficient friction washer 262 is formed of aplurality of arc-shaped members, and is located between the firsthigh-friction-coefficient friction washer 261 and the input frictionplate 263. The first low-friction-coefficient friction washer 262 ispreferably made of plastics. The first low-friction-coefficient frictionwasher 262 has apertures 262 a corresponding to the apertures 271 a.Each aperture 271 a is longer in the rotational direction than theaperture 262 a, and has the opposite ends located circumferentially(i.e., in the rotational direction) outside the aperture 262 a.

The input friction plate 263 has a disk-shaped portion 263 a locatedaxially between the first low-friction-coefficient friction washer 262and the second low-friction-coefficient friction washer 264. The inputfriction plate 263 is provided with a plurality of projections 263 b atits outer periphery as shown in the figure. The projections 263 b areformed corresponding to the recesses 226 a respectively and each areformed of a projected portion 263 c projected radially outward and aclaw 263 d extending axially toward the engine from the end of theprojected portion 263 c. The projected portion 263 c extends radiallythrough the recess 226 a. The claw 263 d is located radially outside thecylindrical portion 226 and extends axially through a recess 220 a inthe cylindrical portion 220 of the disk-shaped member 213 toward theengine. In contrast to the foregoing embodiment, the claw 263 d is incontact with the edge of the recess 220 a without a space in therotational direction.

The input friction plate 263 is provided with apertures 263 e at thedisk-shaped portion 263 a corresponding to the apertures 262 arespectively.

The second low-friction-coefficient friction washer 264 is formed of aplurality of arc-shaped members similar to the firstlow-friction-coefficient friction washer 262, and is located between theinput friction plate 263 and the second high-friction-coefficientfriction washer 265. The second low-friction-coefficient friction washer264 is preferably made of plastics. The second low-friction-coefficientfriction washer 264 is provided with a plurality of first projectedportions 264 a at its surface on the transmission side. Each firstprojected portion 264 a is circumferentially long, and has roundedopposite ends. The first projected portion 264 a is inserted into theaperture 263 e in the disk-shaped portion 263 a, and the end thereof isin contact with the first low-friction-coefficient friction washer 262.The second low-friction-coefficient friction washer 264 has secondprojected portions 264 b, which extend axially toward the transmissionfrom the first projected portions 264 a, respectively. Each secondprojected portion 264 b is circumferentially long and has roundedopposite ends. The second projected portion 264 b is smaller in theradial and circumferential directions than the first projected portion264 a. The second projected portions 264 b are inserted into theapertures 262 a in the first low-friction-coefficient friction washer262 respectively and are engaged therewith in the rotational direction.Owing to this engagement, the first low-friction coefficient frictionwasher 262 rotates together with the second low-friction-coefficientfriction washer 264. Further, the second projected portions 264 b areinserted into the apertures 271 a in the first high-friction-coefficientfriction washer 261, respectively.

The second high-friction-coefficient friction washer 265 is an annularmember, and is located between the second low-friction-coefficientfriction washer 264 and the second friction surface 221 b of theflywheel 221 having the friction surface. The secondhigh-friction-coefficient friction washer 265 is formed of a core plate273 and a friction facing 274 affixed thereto. The core plate 273 is anannular member. The friction facing 274 is formed of a plurality ofarc-shaped members affixed to the surface on the engine side of the coreplate 273, and is in contact with the second friction surface 221 b ofthe flywheel 221 having the friction surface. The core plate 273 isprovided with projected portions 273 a at its body extending axiallytoward the transmission. The projected portions 273 a are inserted intoconcavities 264 c in the second low-friction-coefficient friction washer264.

As shown in FIG. 48, the first projected portions 264 a of the secondlow-friction-coefficient friction washer 264 and the apertures 263 e inthe input friction plate 263 form a first rotating-direction engagementportion 281. In the first rotating-direction engagement portion 281, thecircumferential width of the first projected portion 264 a is shorterthan that of the aperture 263 e. Therefore, the first projected portion264 a can move through a predetermined angle range within the aperture263 e. This means that the input friction plate 263 is movable through apredetermined angle range with respect to the first and secondlow-friction-coefficient friction washers 262 and 264. Morespecifically, a rotating-direction space 246 of a torsion angle of θ1 isensured on the forward side, in the rotational direction R2, of thefirst projected portion 264 a, and a rotating-direction space 247 of atorsion angle of θ2 is formed on the forward side, in the rotationaldirection R1, of the first projected portion 264 a. Consequently, thetotal torsion angle, i.e., the sum of the torsion angles of θ1 and θ2provides the predetermined angle, by which the first and secondlow-friction-coefficient friction washers 262 and 264 can rotaterelatively to the input friction plate 263. In this embodiment, thetotal torsion angle is equal to 8° (see FIG. 42). This total torsionangle is preferably in a range slightly exceeding a damper operationangle, which is caused by minute torsional vibrations due to combustionvariations of the engine.

As seen in FIG. 49, the engagement between the second projected portions264 b of the second low-friction-coefficient friction washer 264 and theapertures 271 a in the first high-friction-coefficient friction washer261 as well as the engagement between the projected portions 273 a ofthe second high-friction-coefficient friction washer 265 and theconcavities 264 c in the second low-friction-coefficient friction washer264 form a second rotating-direction engagement portion 282. Therelationship between the projected portions and the concavities formingthe former engagement is the same or substantially the same as that inthe latter engagement, therefore, the following description will begiven on only the engagement between the second projected portions 264 bof the second low-friction-coefficient friction washer 264 and theapertures 271 a in the first high-friction-coefficient friction washer261 for the sake of simplifying.

In the second rotating-direction engagement portion 282, thecircumferential width of the second projected portion 264 b is shorterthan that of the aperture 271 a, therefore, the second projected portion264 b can move through a predetermined angle range within the aperture271 a. This means that the first and second low-friction-coefficientfriction washers 262 and 264 are movable through a predetermined anglerange with respect to the first and second high-friction-coefficientfriction washers 261 and 265. More specifically, a rotating-directionspace 285 of a torsion angle of θ3 is ensured on the forward side, inthe rotational direction R2, of the second projected portion 264 b, anda rotating-direction space 286 of a torsion angle of θ4 is formed on theforward side, in the rotational direction R1, of the second projectedportion 264 b. Consequently, the total torsion angle, i.e., the sum ofthe torsion angles of θ3 and θ4 provides the predetermined angle, bywhich the first and second low-friction-coefficient friction washers 262and 264 can rotate relatively to the first and secondhigh-friction-coefficient friction washers 261 and 265. In thisembodiment, the total torsion angle is equal to 2° (see FIG. 42).

As seen in FIGS. 46 and 47, the frictional resistance generatingmechanism 207 further includes a bushing 266. The bushing 266 is formedof a plurality of members to support radially the respective washerswith respect to the inner cylindrical portion 228, and is disposedradially between the inner peripheries of the washers and the innercylindrical portion 228. The bushing 266 has a predetermined axiallength, and each portion thereof has an arc-shaped form when viewed inthe axial direction. The bushing 266 has a smooth peripheral surface,which is rotatably supported by an outer peripheral surface 228 b of thefree end portion of the inner cylindrical portion 228.

In the frictional resistance generating mechanism 207 described above,the engagement between the first low-friction-coefficient frictionwasher 262 and the core plate 271 of the first high-friction-coefficientfriction washer 261 as well as the engagement between the secondlow-friction-coefficient friction washer 264 and the core plate 273 ofthe second high-friction-coefficient friction washer 265 provides afirst frictional resistance generating portion 288. Further, a secondfrictional resistance generating portion 289 is provided by theengagement between the first high-friction-coefficient friction washer261 and the output friction plate 244 as well as the engagement betweenthe second high-friction-coefficient friction washer 265 and theflywheel 221 having the friction surface.

(3-2) Operation of Frictional Resistance Generating Mechanism

As seen in FIG. 51, when the clutch device 1 receives the combustionvariations from the engine, the damper mechanism 206 operates to rotatethe input disk-shaped plate 232 relatively to the output disk-shapedplates 230 and 231 so that the plurality of coil springs 233 and othersare compressed are compressed between them. Further, the frictionalresistance generating mechanism 207 generates a predetermined hysteresistorque. Through the foregoing operations, the torsional vibrations areabsorbed and damped. More specifically, the coil springs 233 arecompressed between the circumferential ends of the window apertures inthe input disk-shaped plate 232 and the circumferential ends of thewindows in the output disk-shaped plates 230 and 231.

In the frictional resistance generating mechanism 207, the first andsecond high-friction-coefficient friction washers 261 and 265 rotatetogether with input friction plate 263 with the first and secondlow-friction-coefficient friction washers 262 and 264 therebetween, androtate relatively to the output friction plate 244 and the flywheel 221having the friction surface. Consequently, sliding occurs between theoutput friction plate 244 and the first high-friction-coefficientfriction washer 261, and also occurs between the secondhigh-friction-coefficient friction washer 265 and the flywheel 221having the friction surface. Thus, the second frictional resistancegenerating mechanism 289 operates to generate a relatively largefrictional resistance.

(3-2-1) Minute Torsional Vibrations

Description will now be given on the operation of the damper mechanism206, which is performed when minute torsional vibrations due to thecombustion variations of the engine are applied to the clutch device 1,with reference to a mechanical circuit diagram of FIG. 51 and a torsioncharacteristic diagram of FIG. 42. When minute torsional vibrations areapplied to the damper mechanism 206, in which the coil springs 233 arein the compressed state, the first and second low-friction-coefficientfriction washers 262 and 264 of the frictional resistance generatingmechanism 207 rotate in the minute rotating-direction space (246 and247), which is defined in the aperture 263 e of the input friction plate263 by the first projected portion 264 a of the secondlow-friction-coefficient friction washer 264, and thus rotatesrelatively the input friction plate 263. Thus, input friction plate 263does not drive the first and second low-friction-coefficient frictionwashers 262 and 264, therefore, neither of the first and secondfrictional resistance generating portions 288 and 289 generate africtional resistance (see FIG. 43). Consequently, a high hysteresistorque does not occur in response to the minute torsional vibrations.For example, in “AC2 HYS” illustrated in the torsion characteristicdiagram of FIG. 42, the coil springs 233 operate, but no sliding occursin the frictional resistance generating mechanism 207. In thepredetermined torsion angle range, only a hysteresis torque, which ismuch smaller than an ordinary hysteresis torque, can be obtained. Asdescribed above, the structure employs the minute rotating-directionspace (246 and 247), which does not operate the frictional resistancegenerating mechanism 207 within a predetermined angle range in thetorsion characteristics. Therefore, the levels of the vibrations andnoises can be significantly reduced.

When the torsion angle of the minute torsional vibrations exceeds theangle of the first rotating-direction engagement portion 281, therotating-direction space (246 and 247) disappears in the firstrotating-direction engagement portion 281 and the input friction plate263 drives the first and second low-friction-coefficient frictionwashers 262 and 264 in the rotational direction. Consequently, the firstand second low-friction-coefficient friction washers 262 and 264 rotaterelatively to the first and second high-friction-coefficient frictionwashers 261 and 265. Thus, the first frictional resistance generatingportion 288 operates to generate a relatively small frictionalresistance (see FIG. 44).

When the torsion angle of the torsional vibrations further increases,the circumferential space (285 and 286) in the second rotating-directionengagement portion 282 disappears, and then the first and secondlow-friction-coefficient friction washers 262 and 264 drive the firstand second high-friction-coefficient friction washers 261 and 265 in therotational direction. Thereby, the first and secondhigh-friction-coefficient friction washers 261 and 265 rotate relativelyto the output friction plate 244 and the flywheel 221 having thefriction surface. Thus, the second frictional resistance generatingportion 289 operates to generate a relatively large frictionalresistance (see FIG. 45).

(3-2-2) Large-Angle Torsional Vibrations

As already described, when the torsion angle of the torsional vibrationsis large, sliding occurs between the output friction plate 244 and thefirst high-friction-coefficient friction washer 261 and sliding alsooccurs between the second high-friction-coefficient friction washer 265and the flywheel 221 having the friction surface.

At an end of the torsion angle range (i.e., the position where thedirection of the vibration changes), operations are performed asfollows. On the right end in the torsion characteristic diagram of FIG.42, the first and second low-friction-coefficient friction washers 262and 264 are in the positions shifted in the rotational direction R2 tothe maximum extent with respect to the input friction plate 263, and thefirst and second high-friction-coefficient friction washers 261 and 265are in the positions shifted in the rotational direction R2 to themaximum extent with respect to the first and secondlow-friction-coefficient friction washers 262 and 264. When the inputfriction plate 263 rotates relatively to the flywheel 221 having thefriction surface in the rotational direction R2, the input frictionplate 263 angularly moves throughout the rotating-direction space (246and 247) of the first rotating-direction engagement portion 281 androtates relatively to the first and second low-friction-coefficientfriction washers 262 and 264. During this operation, neither of thefirst and second frictional resistance generating portions 288 and 289generates the frictional resistance. When the rotating-direction space(246 and 247) in the first rotating-direction engagement portion 281disappears, the first and second low-friction-coefficient frictionwashers 262 and 264 drive the first and second high-friction-coefficientfriction washers 261 and 265. Thereby, the first and secondlow-friction-coefficient friction washers 262 and 264 angularly movethroughout the rotating-direction space (285 and 286) in the secondrotating-direction engagement portion 282, and rotate relatively to thefirst and second high-friction-coefficient friction washers 261 and 265.During this operation, the first frictional resistance generatingportion 288 operates to generate a relatively small frictionalresistance.

When the rotating-direction space (285 and 286) in the secondrotating-direction engagement portion 282 disappears, the first andsecond low-friction-coefficient friction washers 262 and 264 drive thefirst and second high-friction-coefficient friction washers 261 and 265.Thereby, the first and second high-friction-coefficient friction washers261 and 265 rotate relatively to the output friction plate 244 and theflywheel 221 having the friction surface. Thereby, the second frictionalresistance generating portion 289 operates to generate a largefrictional resistance.

As described above, the first frictional resistance generating portion288 generates a frictional resistance of an intermediate magnitudewithin the torsion angle range of the rotating-direction space (285 and286) in the second rotating-direction engagement portion 282 before thesecond frictional resistance generating portion 289 operates to generatea large frictional resistance. As described above, the large frictionalresistance rises in a multi-step or stepwise fashion so that a wall of ahigh hysteresis torque does not exist when generating the largefrictional resistance. Thereby, hitting or tapping noises of claws,which may occur when a high hysteresis torque occurs, can be reduced inthe frictional resistance generating mechanism, which is provided withthe minute space in the rotational direction for absorbing the minutetorsional vibrations.

In the frictional resistance generating mechanism 207, therotating-direction space (246 and 247) in the first rotating-directionengagement portion 281 is not located radially outside an area, in whichthe first and second low-friction-coefficient friction washers 262 and264 axially overlap with the first and second high-friction-coefficientfriction washers 261 and 265. Therefore, the whole structure can berelatively compact.

In this frictional resistance generating mechanism 207, therotating-direction space (246 and 247) in the first rotating-directionengagement portion 281 is formed between the secondlow-friction-coefficient friction washer 264 and the disk-shaped portion263 a of the input friction plate 263. Therefore, the structureproviding the rotating-direction space (246 and 247) becomes simpler.This improves the accuracy of the rotating-direction space.

Fourth Embodiment

Referring to a mechanical circuit diagram of FIG. 52, description willnow be given on a frictional resistance generating mechanism 307 in thefourth embodiment.

The frictional resistance generating mechanism 307 includes a firstrotary member 363, a second rotary member 330, a first intermediatemember 362, and a second intermediate member 372. The first and secondrotary members 363 and 330 are rotatable relatively to each other, andare coupled together in the rotational direction by elastic members (notshown). The first and second intermediate members 362 and 372 aredisposed between the first and second rotary members 363 and 330 tooperate in series in the rotational direction. The first intermediatemember 362 is engaged with the first rotary member 363 via a firstrotating-direction space forming portion 381 and is further engaged withthe second intermediate member 372 via a second rotating-direction spaceforming portion 382. The first intermediate member 362 is frictionallyengaged with the second rotary member 330 via a first frictiongenerating portion 388. The second intermediate member 372 isfrictionally engaged with the second rotary member 330 via a secondfriction generating portion 389. As described above, the first andsecond friction generating portions 388 and 389 are disposedcircumferentially between the first and second rotary members 363 and330 to operate in parallel with each other.

Referring to the mechanical circuit diagram of FIG. 52 and a torsioncharacteristic diagram of FIG. 53, description will now be given on anoperation of this frictional resistance generating mechanism 307, inwhich the first rotary member 363 rotates relatively to the secondrotary member 330.

In an initial torsion stage, neither of the first and second frictiongenerating portions 388 and 389 operates owing to the rotating-directionspace in the first rotating-direction space forming portion 381. Thisprovides a region, where a hysteresis torque hardly occurs.

When the rotating-direction space in the first rotating-direction spaceforming portion 381 disappears, the first rotary member 363 starts todrive the first intermediate member 362 in the rotational direction. Inthis operation, the first friction generating portion 388 operates togenerate a predetermined frictional resistance (DC1 in FIG. 53). In thisoperation, the second friction generating portion 389 does not operateowing to the second rotating direction space forming portion 382.

When the rotating-direction space in the second rotating-direction spaceforming portion 382 disappears, the first intermediate member 362 drivesthe second intermediate member 372 in the rotational direction. In thisoperation, the second friction generating portion 389 operates togenerate a predetermined frictional resistance (DC2 in FIG. 53). Duringthis operation, the first friction generating portion 388 is alsooperating so that a frictional resistance produced in this state islarger than that produced when only the first friction generatingportion 388 is operating.

As described above, the large frictional resistance rises in amulti-step or stepwise fashion so that a wall of a high hysteresistorque does not exist when generating the large frictional resistance.Thereby, hitting or tapping noises of claws, which may occur when a highhysteresis torque occurs, can be reduced in the frictional resistancegenerating mechanism.

Fifth Embodiment

Referring to a mechanical circuit diagram of FIG. 54, description willnow be given on a frictional resistance generating mechanism 307′ in afifth embodiment.

The frictional resistance generating mechanism 307′ includes the firstrotary member 363, the second rotary member 330, the first intermediatemember 362, a second intermediate member 372′, and a third intermediatemember 385. The first and second rotary members 363 and 330 arerotatable relatively to each other and are coupled together in therotational direction by elastic members (not shown). The first, secondand third intermediate members 362, 372′, and 385 are disposed betweenthe first and second rotary members 363 and 330 to operate in series inthe rotational direction. The first intermediate member 362 is engagedwith the first rotary member 363 via the first rotating-direction spaceforming portion 381, and is engaged with the second intermediate member372′ via the second rotating-direction space forming portion 382. Thesecond intermediate member 372′ is engaged with the third intermediatemember 385 via a third rotating-direction space forming portion 383. Thefirst intermediate member 362 is frictionally engaged with the secondrotary member 330 via the first friction generating portion 388. Thesecond intermediate member 372′ is frictionally engaged with the secondrotary member 330 via the second friction generating portion 389. Thethird intermediate member 385 is frictionally engaged with the secondrotary member 330 via a third friction generating portion 390. Asdescribed above, the first, second and third friction generatingportions 388, 389, and 390 are disposed circumferentially between thefirst and second rotary members 363 and 330 to operate in parallel witheach other.

Referring to the mechanical circuit diagram of FIG. 54 and a torsioncharacteristic diagram of FIG. 55, description will now be given on anoperation of this frictional resistance generating mechanism 307′, inwhich the first rotary member 363 rotates relatively to the secondrotary member 330.

In an initial torsion stage, any one of the first, second and thirdfriction generating portions 388, 389, and 390 does not operate owing tothe rotating-direction space in the first rotating-direction spaceforming portion 381. This provides a region, where a hysteresis torquehardly occurs.

When the rotating-direction space in the first rotating-direction spaceforming portion 381 disappears, the first rotary member 363 starts todrive the first intermediate member 362 in the rotational direction. Inthis operation, the first friction generating portion 388 operates togenerate a predetermined frictional resistance (DC1 in FIG. 55). In thisoperation, the second friction generating portion 389 does not operateowing to the second rotating-direction space forming portion 382, andthe third friction generating portion 390 does not operate owing to thethird rotating-direction space forming portion 383.

When the rotating-direction space in the second rotating-direction spaceforming portion 382 disappears, the first intermediate member 362 drivesthe second intermediate member 372′ in the rotational direction. In thisoperation, the second friction generating portion 389 operates togenerate a predetermined frictional resistance (DC2 in FIG. 55). Duringthis operation, the first friction generating portion 388 is alsooperating so that both the friction generating portions produce africtional resistance larger than that, which is produced when only thefirst friction generating portion 388 is operating. In this operation,the third friction generating portion 390 does not operate owing to thethird rotating-direction space forming portion 383.

When the rotating-direction space in the third rotating-direction spaceforming portion 383 disappears, the second intermediate member 372′drives the third intermediate member 385 in the rotational direction. Inthis operation, the third friction generating portion 390 operates togenerate a predetermined frictional resistance (DC3 in FIG. 55). Duringthis operation, the first and second friction generating portions 388and 389 are also operating so that the friction generating portionsproduce a frictional resistance larger than that which is produced whenonly the first and second friction generating portions 388 and 389 areoperating.

In this embodiment, since the large frictional resistance occurs throughthree stages, the wall of the large hysteresis torque, which may occurwhen generating the large frictional resistance, can be further small sothat hitting or tapping noises of claws can be further reduced in thefrictional resistance generating mechanism when generating the highhysteresis torque.

The large frictional resistance may be configured to rise through fouror more stages.

Sixth Embodiment

As illustrated in FIG. 56, the large frictional resistance may be raisedsmoothly instead of a multi-step fashion. In other words, anintermediate frictional resistance may be raised gradually beforegenerating a large frictional resistance. In FIG. 56, a solid linerepresents a linear change in intermediate frictional resistance.Further, broken lines in FIG. 56 represent a manner, in which anincreasing rate of the torque with respect to the angle decreases withangle, and a manner, in which the above rate increases with angle.

Other Embodiments

Although the embodiments of the clutch devices according to the presentinvention have been described and illustrated in detail, the inventionis not restricted to such embodiments and can be variously modified orchanged without departing from the scope of the invention.

In the damper mechanism according to the invention, therotating-direction space in the frictional resistance suppressingmechanism prevents the operation of the frictional resistance generatingmechanism in both the ranges of small and large torsion angles of minutetorsional vibrations. Thus, a large frictional resistance does not occurin response to minute torsional vibrations in the first stage of thetorsion characteristics so that torsional vibration damping performancesare improved.

EFFECT OF THE INVENTION

In the frictional resistance generating mechanism according to thepresent invention, when the torsion angle of the torsional vibrations iswithin the angle range of the first rotating-direction space in thefirst frictional resistance suppressing portion, the firstrotating-direction space prevents the operations of the first and secondfrictional resistance generating portions so that a large frictionalresistance does not occur. When the torsion angle of the torsionalvibrations is within the angle range of the second rotating-directionspace of the second frictional resistance suppressing portion, thesecond rotating-direction space operates only the first frictionalresistance generating portion to generate a frictional resistance of anintermediate magnitude. When the torsion angle of the torsionalvibrations exceeds the angle range of the second rotating-directionspace, the second frictional resistance generating portion operates togenerate the largest frictional resistance.

As described above, the first frictional resistance generating portiongenerates the frictional resistance of an intermediate magnitude in thetorsion angle range of the second rotating-direction space before thesecond frictional resistance generating portion operates to generate thelarge frictional resistance. In this manner, the large frictionalresistance rises in a multi-step or stepwise fashion so that a wall of ahigh hysteresis torque does not exist when the large frictionalresistance is generated. Thereby, hitting or tapping noises of claws,which may occur when a high hysteresis torque occurs, can be reduced inthe frictional resistance generating mechanism

In the flywheel assembly according to the invention, the plate-likecoupling portion is radially shorter than the conventional stop pin, andtherefore can be arranged in the radially outermost position of thesecond disk-shaped plate. Accordingly, the plate-like coupling portiondoes not interfere with the elastic member so that the torsion angle ofthe damper mechanism can be sufficiently increased.

As used herein, the following directional terms “forward, rearward,above, downward, vertical, horizontal, below, and transverse” as well asany other similar directional terms refer to those directions of avehicle equipped with the present invention. Accordingly, these terms,as utilized to describe the present invention should be interpretedrelative to a vehicle equipped with the present invention.

Terms that are expressed as “means-plus function” in the claims shouldinclude any structure that can be utilized to carry out the function ofthat part of the present invention.

The terms of degree such as “substantially,” “about,” and“approximately” as used herein mean a reasonable amount of deviation ofthe modified term such that the end result is not significantly changed.For example, these terms can be construed as including a deviation of atleast ±5% of the modified term if this deviation would not negate themeaning of the word it modifies.

This application claims priority to Japanese Patent Applications Nos.2002-307250, 2002-307251, 2002-351589, and 2003-162896. The entiredisclosures of Japanese Patent Application Applications Nos.2002-307250, 2002-307251, 2002-351589, and 2003-162896 are herebyincorporated herein by reference.

While only selected embodiments have been chosen to illustrate thepresent invention, it will be apparent to those skilled in the art fromthis disclosure that various changes and modifications can be madeherein without departing from the scope of the invention as defined inthe appended claims. Furthermore, the foregoing descriptions of theembodiments according to the present invention are provided forillustration only, and not for the purpose of limiting the invention asdefined by the appended claims and their equivalents. Thus, the scope ofthe invention is not limited to the disclosed embodiments.

1. A flywheel assembly for transmitting a torque from a crankshaft of anengine, comprising: a flywheel having a friction surface; an elasticcoupling mechanism being configured to couple elastically said flywheeland the crankshaft in a rotating direction, and having a pair of firstdisk-shaped members being axially spaced from each other and fixedtogether, said pair of first disk-shaped members being fixedly coupledto said flywheel, a second disk-shaped member being arranged betweensaid pair of first disk-shaped members, and an elastic member beingconfigured to couple elastically said first disk-shaped members to saidsecond disk-shaped member in said rotating direction; and a platecoupling portion extending between outer peripheries of said pairedfirst disk-shaped members, and fixing said pair of first disk-shapedmembers together.
 2. The flywheel assembly according to claim 1, whereinsaid plate coupling portion is arranged at a plurality ofcircumferentially shifted positions.
 3. The flywheel assembly accordingto claim 2, wherein said plate coupling portion has main surfacesdirected radially inward and outward, respectively.
 4. The flywheelassembly according to claim 3, wherein said plate coupling portionextends integrally from one of said pair of first disk-shaped members.5. The flywheel assembly according to claim 4, wherein said seconddisk-shaped member is provided with a stop portion that is arranged tocollide in the rotational direction with said plate coupling portionwhen a torsion angle between said pair of first disk-shaped members andsaid second disk-shaped member increases.
 6. The flywheel assemblyaccording to claim 1, wherein said plate coupling portion has mainsurfaces directed radially inward and outward, respectively.
 7. Theflywheel assembly according to claim 1, wherein said plate couplingportion extends integrally from one of said pair of first disk-shapedmembers.
 8. The flywheel assembly according to claim 7, wherein saidsecond disk-shaped member is provided with a stop portion that isarranged to collide in the rotational direction with said plate couplingportion when a torsion angle between said pair of first disk-shapedmembers and said second disk-shaped member increases.
 9. The flywheelassembly according to claim 1, wherein said second disk-shaped member isprovided with a stop portion that is arranged to collide in therotational direction with said plate coupling portion when a torsionangle between said pair of first disk-shaped members and said seconddisk-shaped member increases.
 10. The flywheel assembly according toclaim 1, wherein said pair of first disk-shaped members is fixedlycoupled to said flywheel by a nut and a bolt.
 11. The flywheel assemblyaccording to claim 1, wherein at least one of said pair of firstdisk-shaped members is fixed to said plate coupling portion by a rivet.12. The flywheel assembly according to claim 11, wherein the other ofsaid pair of first disk-shaped members has a rivet aperture, and saidsecond disk-shaped member has a recess through which said rivet isconfigured to pass.